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2022-04-27sched/pelt: Fix attach_entity_load_avg() corner casekuyo chang
[ Upstream commit 40f5aa4c5eaebfeaca4566217cb9c468e28ed682 ] The warning in cfs_rq_is_decayed() triggered: SCHED_WARN_ON(cfs_rq->avg.load_avg || cfs_rq->avg.util_avg || cfs_rq->avg.runnable_avg) There exists a corner case in attach_entity_load_avg() which will cause load_sum to be zero while load_avg will not be. Consider se_weight is 88761 as per the sched_prio_to_weight[] table. Further assume the get_pelt_divider() is 47742, this gives: se->avg.load_avg is 1. However, calculating load_sum: se->avg.load_sum = div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se)); se->avg.load_sum = 1*47742/88761 = 0. Then enqueue_load_avg() adds this to the cfs_rq totals: cfs_rq->avg.load_avg += se->avg.load_avg; cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum; Resulting in load_avg being 1 with load_sum is 0, which will trigger the WARN. Fixes: f207934fb79d ("sched/fair: Align PELT windows between cfs_rq and its se") Signed-off-by: kuyo chang <kuyo.chang@mediatek.com> [peterz: massage changelog] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lkml.kernel.org/r/20220414090229.342-1-kuyo.chang@mediatek.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-04-08sched/core: Export pelt_thermal_tpQais Yousef
[ Upstream commit 77cf151b7bbdfa3577b3c3f3a5e267a6c60a263b ] We can't use this tracepoint in modules without having the symbol exported first, fix that. Fixes: 765047932f15 ("sched/pelt: Add support to track thermal pressure") Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20211028115005.873539-1-qais.yousef@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-04-08sched/debug: Remove mpol_get/put and task_lock/unlock from sched_show_numaBharata B Rao
[ Upstream commit 28c988c3ec29db74a1dda631b18785958d57df4f ] The older format of /proc/pid/sched printed home node info which required the mempolicy and task lock around mpol_get(). However the format has changed since then and there is no need for sched_show_numa() any more to have mempolicy argument, asssociated mpol_get/put and task_lock/unlock. Remove them. Fixes: 397f2378f1361 ("sched/numa: Fix numa balancing stats in /proc/pid/sched") Signed-off-by: Bharata B Rao <bharata@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Mel Gorman <mgorman@suse.de> Link: https://lore.kernel.org/r/20220118050515.2973-1-bharata@amd.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-03-08sched/topology: Fix sched_domain_topology_level alloc in sched_init_numa()Dietmar Eggemann
commit 71e5f6644fb2f3304fcb310145ded234a37e7cc1 upstream. Commit "sched/topology: Make sched_init_numa() use a set for the deduplicating sort" allocates 'i + nr_levels (level)' instead of 'i + nr_levels + 1' sched_domain_topology_level. This led to an Oops (on Arm64 juno with CONFIG_SCHED_DEBUG): sched_init_domains build_sched_domains() __free_domain_allocs() __sdt_free() { ... for_each_sd_topology(tl) ... sd = *per_cpu_ptr(sdd->sd, j); <-- ... } Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Barry Song <song.bao.hua@hisilicon.com> Link: https://lkml.kernel.org/r/6000e39e-7d28-c360-9cd6-8798fd22a9bf@arm.com Signed-off-by: dann frazier <dann.frazier@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-03-08sched/topology: Make sched_init_numa() use a set for the deduplicating sortValentin Schneider
commit 620a6dc40754dc218f5b6389b5d335e9a107fd29 upstream. The deduplicating sort in sched_init_numa() assumes that the first line in the distance table contains all unique values in the entire table. I've been trying to pen what this exactly means for the topology, but it's not straightforward. For instance, topology.c uses this example: node 0 1 2 3 0: 10 20 20 30 1: 20 10 20 20 2: 20 20 10 20 3: 30 20 20 10 0 ----- 1 | / | | / | | / | 2 ----- 3 Which works out just fine. However, if we swap nodes 0 and 1: 1 ----- 0 | / | | / | | / | 2 ----- 3 we get this distance table: node 0 1 2 3 0: 10 20 20 20 1: 20 10 20 30 2: 20 20 10 20 3: 20 30 20 10 Which breaks the deduplicating sort (non-representative first line). In this case this would just be a renumbering exercise, but it so happens that we can have a deduplicating sort that goes through the whole table in O(n²) at the extra cost of a temporary memory allocation (i.e. any form of set). The ACPI spec (SLIT) mentions distances are encoded on 8 bits. Following this, implement the set as a 256-bits bitmap. Should this not be satisfactory (i.e. we want to support 32-bit values), then we'll have to go for some other sparse set implementation. This has the added benefit of letting us allocate just the right amount of memory for sched_domains_numa_distance[], rather than an arbitrary (nr_node_ids + 1). Note: DT binding equivalent (distance-map) decodes distances as 32-bit values. Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210122123943.1217-2-valentin.schneider@arm.com Signed-off-by: dann frazier <dann.frazier@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-02-05psi: Fix uaf issue when psi trigger is destroyed while being polledSuren Baghdasaryan
commit a06247c6804f1a7c86a2e5398a4c1f1db1471848 upstream. With write operation on psi files replacing old trigger with a new one, the lifetime of its waitqueue is totally arbitrary. Overwriting an existing trigger causes its waitqueue to be freed and pending poll() will stumble on trigger->event_wait which was destroyed. Fix this by disallowing to redefine an existing psi trigger. If a write operation is used on a file descriptor with an already existing psi trigger, the operation will fail with EBUSY error. Also bypass a check for psi_disabled in the psi_trigger_destroy as the flag can be flipped after the trigger is created, leading to a memory leak. Fixes: 0e94682b73bf ("psi: introduce psi monitor") Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Analyzed-by: Eric Biggers <ebiggers@kernel.org> Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Eric Biggers <ebiggers@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220111232309.1786347-1-surenb@google.com [surenb: backported to 5.10 kernel] CC: stable@vger.kernel.org # 5.10 Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-02-01sched/pelt: Relax the sync of util_sum with util_avgVincent Guittot
[ Upstream commit 98b0d890220d45418cfbc5157b3382e6da5a12ab ] Rick reported performance regressions in bugzilla because of cpu frequency being lower than before: https://bugzilla.kernel.org/show_bug.cgi?id=215045 He bisected the problem to: commit 1c35b07e6d39 ("sched/fair: Ensure _sum and _avg values stay consistent") This commit forces util_sum to be synced with the new util_avg after removing the contribution of a task and before the next periodic sync. By doing so util_sum is rounded to its lower bound and might lost up to LOAD_AVG_MAX-1 of accumulated contribution which has not yet been reflected in util_avg. Instead of always setting util_sum to the low bound of util_avg, which can significantly lower the utilization of root cfs_rq after propagating the change down into the hierarchy, we revert the change of util_sum and propagate the difference. In addition, we also check that cfs's util_sum always stays above the lower bound for a given util_avg as it has been observed that sched_entity's util_sum is sometimes above cfs one. Fixes: 1c35b07e6d39 ("sched/fair: Ensure _sum and _avg values stay consistent") Reported-by: Rick Yiu <rickyiu@google.com> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Sachin Sant <sachinp@linux.ibm.com> Link: https://lkml.kernel.org/r/20220111134659.24961-2-vincent.guittot@linaro.org Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-02-01kernel: delete repeated words in commentsRandy Dunlap
[ Upstream commit c034f48e99907d5be147ac8f0f3e630a9307c2be ] Drop repeated words in kernel/events/. {if, the, that, with, time} Drop repeated words in kernel/locking/. {it, no, the} Drop repeated words in kernel/sched/. {in, not} Link: https://lkml.kernel.org/r/20210127023412.26292-1-rdunlap@infradead.org Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Acked-by: Will Deacon <will@kernel.org> [kernel/locking/] Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Will Deacon <will@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-02-01sched/membarrier: Fix membarrier-rseq fence command missing from query bitmaskMathieu Desnoyers
commit 809232619f5b15e31fb3563985e705454f32621f upstream. The membarrier command MEMBARRIER_CMD_QUERY allows querying the available membarrier commands. When the membarrier-rseq fence commands were added, a new MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK was introduced with the intent to expose them with the MEMBARRIER_CMD_QUERY command, the but it was never added to MEMBARRIER_CMD_BITMASK. The membarrier-rseq fence commands are therefore not wired up with the query command. Rename MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK to MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK (the bitmask is not a command per-se), and change the erroneous MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ_BITMASK (which does not actually exist) to MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ. Wire up MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK in MEMBARRIER_CMD_BITMASK. Fixing this allows discovering availability of the membarrier-rseq fence feature. Fixes: 2a36ab717e8f ("rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ") Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <stable@vger.kernel.org> # 5.10+ Link: https://lkml.kernel.org/r/20220117203010.30129-1-mathieu.desnoyers@efficios.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-01-27cputime, cpuacct: Include guest time in user time in cpuacct.statAndrey Ryabinin
commit 9731698ecb9c851f353ce2496292ff9fcea39dff upstream. cpuacct.stat in no-root cgroups shows user time without guest time included int it. This doesn't match with user time shown in root cpuacct.stat and /proc/<pid>/stat. This also affects cgroup2's cpu.stat in the same way. Make account_guest_time() to add user time to cgroup's cpustat to fix this. Fixes: ef12fefabf94 ("cpuacct: add per-cgroup utime/stime statistics") Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20211115164607.23784-1-arbn@yandex-team.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-01-27sched/rt: Try to restart rt period timer when rt runtime exceededLi Hua
[ Upstream commit 9b58e976b3b391c0cf02e038d53dd0478ed3013c ] When rt_runtime is modified from -1 to a valid control value, it may cause the task to be throttled all the time. Operations like the following will trigger the bug. E.g: 1. echo -1 > /proc/sys/kernel/sched_rt_runtime_us 2. Run a FIFO task named A that executes while(1) 3. echo 950000 > /proc/sys/kernel/sched_rt_runtime_us When rt_runtime is -1, The rt period timer will not be activated when task A enqueued. And then the task will be throttled after setting rt_runtime to 950,000. The task will always be throttled because the rt period timer is not activated. Fixes: d0b27fa77854 ("sched: rt-group: synchonised bandwidth period") Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Li Hua <hucool.lihua@huawei.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20211203033618.11895-1-hucool.lihua@huawei.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-01-27sched/fair: Fix per-CPU kthread and wakee stacking for asym CPU capacityVincent Donnefort
[ Upstream commit 014ba44e8184e1acf93e0cbb7089ee847802f8f0 ] select_idle_sibling() has a special case for tasks woken up by a per-CPU kthread where the selected CPU is the previous one. For asymmetric CPU capacity systems, the assumption was that the wakee couldn't have a bigger utilization during task placement than it used to have during the last activation. That was not considering uclamp.min which can completely change between two task activations and as a consequence mandates the fitness criterion asym_fits_capacity(), even for the exit path described above. Fixes: b4c9c9f15649 ("sched/fair: Prefer prev cpu in asymmetric wakeup path") Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lkml.kernel.org/r/20211129173115.4006346-1-vincent.donnefort@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-01-27sched/fair: Fix detection of per-CPU kthreads waking a taskVincent Donnefort
[ Upstream commit 8b4e74ccb582797f6f0b0a50372ebd9fd2372a27 ] select_idle_sibling() has a special case for tasks woken up by a per-CPU kthread, where the selected CPU is the previous one. However, the current condition for this exit path is incomplete. A task can wake up from an interrupt context (e.g. hrtimer), while a per-CPU kthread is running. A such scenario would spuriously trigger the special case described above. Also, a recent change made the idle task like a regular per-CPU kthread, hence making that situation more likely to happen (is_per_cpu_kthread(swapper) being true now). Checking for task context makes sure select_idle_sibling() will not interpret a wake up from any other context as a wake up by a per-CPU kthread. Fixes: 52262ee567ad ("sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression") Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lore.kernel.org/r/20211201143450.479472-1-vincent.donnefort@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-12-14wait: add wake_up_pollfree()Eric Biggers
commit 42288cb44c4b5fff7653bc392b583a2b8bd6a8c0 upstream. Several ->poll() implementations are special in that they use a waitqueue whose lifetime is the current task, rather than the struct file as is normally the case. This is okay for blocking polls, since a blocking poll occurs within one task; however, non-blocking polls require another solution. This solution is for the queue to be cleared before it is freed, using 'wake_up_poll(wq, EPOLLHUP | POLLFREE);'. However, that has a bug: wake_up_poll() calls __wake_up() with nr_exclusive=1. Therefore, if there are multiple "exclusive" waiters, and the wakeup function for the first one returns a positive value, only that one will be called. That's *not* what's needed for POLLFREE; POLLFREE is special in that it really needs to wake up everyone. Considering the three non-blocking poll systems: - io_uring poll doesn't handle POLLFREE at all, so it is broken anyway. - aio poll is unaffected, since it doesn't support exclusive waits. However, that's fragile, as someone could add this feature later. - epoll doesn't appear to be broken by this, since its wakeup function returns 0 when it sees POLLFREE. But this is fragile. Although there is a workaround (see epoll), it's better to define a function which always sends POLLFREE to all waiters. Add such a function. Also make it verify that the queue really becomes empty after all waiters have been woken up. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211209010455.42744-2-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-12-08sched/uclamp: Fix rq->uclamp_max not set on first enqueueQais Yousef
[ Upstream commit 315c4f884800c45cb6bd8c90422fad554a8b9588 ] Commit d81ae8aac85c ("sched/uclamp: Fix initialization of struct uclamp_rq") introduced a bug where uclamp_max of the rq is not reset to match the woken up task's uclamp_max when the rq is idle. The code was relying on rq->uclamp_max initialized to zero, so on first enqueue static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p, enum uclamp_id clamp_id) { ... if (uc_se->value > READ_ONCE(uc_rq->value)) WRITE_ONCE(uc_rq->value, uc_se->value); } was actually resetting it. But since commit d81ae8aac85c changed the default to 1024, this no longer works. And since rq->uclamp_flags is also initialized to 0, neither above code path nor uclamp_idle_reset() update the rq->uclamp_max on first wake up from idle. This is only visible from first wake up(s) until the first dequeue to idle after enabling the static key. And it only matters if the uclamp_max of this task is < 1024 since only then its uclamp_max will be effectively ignored. Fix it by properly initializing rq->uclamp_flags = UCLAMP_FLAG_IDLE to ensure uclamp_idle_reset() is called which then will update the rq uclamp_max value as expected. Fixes: d81ae8aac85c ("sched/uclamp: Fix initialization of struct uclamp_rq") Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lkml.kernel.org/r/20211202112033.1705279-1-qais.yousef@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-12-01sched/scs: Reset task stack state in bringup_cpu()Mark Rutland
[ Upstream commit dce1ca0525bfdc8a69a9343bc714fbc19a2f04b3 ] To hot unplug a CPU, the idle task on that CPU calls a few layers of C code before finally leaving the kernel. When KASAN is in use, poisoned shadow is left around for each of the active stack frames, and when shadow call stacks are in use. When shadow call stacks (SCS) are in use the task's saved SCS SP is left pointing at an arbitrary point within the task's shadow call stack. When a CPU is offlined than onlined back into the kernel, this stale state can adversely affect execution. Stale KASAN shadow can alias new stackframes and result in bogus KASAN warnings. A stale SCS SP is effectively a memory leak, and prevents a portion of the shadow call stack being used. Across a number of hotplug cycles the idle task's entire shadow call stack can become unusable. We previously fixed the KASAN issue in commit: e1b77c92981a5222 ("sched/kasan: remove stale KASAN poison after hotplug") ... by removing any stale KASAN stack poison immediately prior to onlining a CPU. Subsequently in commit: f1a0a376ca0c4ef1 ("sched/core: Initialize the idle task with preemption disabled") ... the refactoring left the KASAN and SCS cleanup in one-time idle thread initialization code rather than something invoked prior to each CPU being onlined, breaking both as above. We fixed SCS (but not KASAN) in commit: 63acd42c0d4942f7 ("sched/scs: Reset the shadow stack when idle_task_exit") ... but as this runs in the context of the idle task being offlined it's potentially fragile. To fix these consistently and more robustly, reset the SCS SP and KASAN shadow of a CPU's idle task immediately before we online that CPU in bringup_cpu(). This ensures the idle task always has a consistent state when it is running, and removes the need to so so when exiting an idle task. Whenever any thread is created, dup_task_struct() will give the task a stack which is free of KASAN shadow, and initialize the task's SCS SP, so there's no need to specially initialize either for idle thread within init_idle(), as this was only necessary to handle hotplug cycles. I've tested this on arm64 with: * gcc 11.1.0, defconfig +KASAN_INLINE, KASAN_STACK * clang 12.0.0, defconfig +KASAN_INLINE, KASAN_STACK, SHADOW_CALL_STACK ... offlining and onlining CPUS with: | while true; do | for C in /sys/devices/system/cpu/cpu*/online; do | echo 0 > $C; | echo 1 > $C; | done | done Fixes: f1a0a376ca0c4ef1 ("sched/core: Initialize the idle task with preemption disabled") Reported-by: Qian Cai <quic_qiancai@quicinc.com> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Tested-by: Qian Cai <quic_qiancai@quicinc.com> Link: https://lore.kernel.org/lkml/20211115113310.35693-1-mark.rutland@arm.com/ Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-11-26sched/core: Mitigate race cpus_share_cache()/update_top_cache_domain()Vincent Donnefort
[ Upstream commit 42dc938a590c96eeb429e1830123fef2366d9c80 ] Nothing protects the access to the per_cpu variable sd_llc_id. When testing the same CPU (i.e. this_cpu == that_cpu), a race condition exists with update_top_cache_domain(). One scenario being: CPU1 CPU2 ================================================================== per_cpu(sd_llc_id, CPUX) => 0 partition_sched_domains_locked() detach_destroy_domains() cpus_share_cache(CPUX, CPUX) update_top_cache_domain(CPUX) per_cpu(sd_llc_id, CPUX) => 0 per_cpu(sd_llc_id, CPUX) = CPUX per_cpu(sd_llc_id, CPUX) => CPUX return false ttwu_queue_cond() wouldn't catch smp_processor_id() == cpu and the result is a warning triggered from ttwu_queue_wakelist(). Avoid a such race in cpus_share_cache() by always returning true when this_cpu == that_cpu. Fixes: 518cd6234178 ("sched: Only queue remote wakeups when crossing cache boundaries") Reported-by: Jing-Ting Wu <jing-ting.wu@mediatek.com> Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20211104175120.857087-1-vincent.donnefort@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-11-18kernel/sched: Fix sched_fork() access an invalid sched_task_groupZhang Qiao
[ Upstream commit 4ef0c5c6b5ba1f38f0ea1cedad0cad722f00c14a ] There is a small race between copy_process() and sched_fork() where child->sched_task_group point to an already freed pointer. parent doing fork() | someone moving the parent | to another cgroup -------------------------------+------------------------------- copy_process() + dup_task_struct()<1> parent move to another cgroup, and free the old cgroup. <2> + sched_fork() + __set_task_cpu()<3> + task_fork_fair() + sched_slice()<4> In the worst case, this bug can lead to "use-after-free" and cause panic as shown above: (1) parent copy its sched_task_group to child at <1>; (2) someone move the parent to another cgroup and free the old cgroup at <2>; (3) the sched_task_group and cfs_rq that belong to the old cgroup will be accessed at <3> and <4>, which cause a panic: [] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [] PGD 8000001fa0a86067 P4D 8000001fa0a86067 PUD 2029955067 PMD 0 [] Oops: 0000 [#1] SMP PTI [] CPU: 7 PID: 648398 Comm: ebizzy Kdump: loaded Tainted: G OE --------- - - 4.18.0.x86_64+ #1 [] RIP: 0010:sched_slice+0x84/0xc0 [] Call Trace: [] task_fork_fair+0x81/0x120 [] sched_fork+0x132/0x240 [] copy_process.part.5+0x675/0x20e0 [] ? __handle_mm_fault+0x63f/0x690 [] _do_fork+0xcd/0x3b0 [] do_syscall_64+0x5d/0x1d0 [] entry_SYSCALL_64_after_hwframe+0x65/0xca [] RIP: 0033:0x7f04418cd7e1 Between cgroup_can_fork() and cgroup_post_fork(), the cgroup membership and thus sched_task_group can't change. So update child's sched_task_group at sched_post_fork() and move task_fork() and __set_task_cpu() (where accees the sched_task_group) from sched_fork() to sched_post_fork(). Fixes: 8323f26ce342 ("sched: Fix race in task_group") Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lkml.kernel.org/r/20210915064030.2231-1-zhangqiao22@huawei.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-10-27sched/scs: Reset the shadow stack when idle_task_exitWoody Lin
[ Upstream commit 63acd42c0d4942f74710b11c38602fb14dea7320 ] Commit f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled") removed the init_idle() call from idle_thread_get(). This was the sole call-path on hotplug that resets the Shadow Call Stack (scs) Stack Pointer (sp). Not resetting the scs-sp leads to scs overflow after enough hotplug cycles. Therefore add an explicit scs_task_reset() to the hotplug code to make sure the scs-sp does get reset on hotplug. Fixes: f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled") Signed-off-by: Woody Lin <woodylin@google.com> [peterz: Changelog] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lore.kernel.org/r/20211012083521.973587-1-woodylin@google.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-10-06cpufreq: schedutil: Use kobject release() method to free sugov_tunablesKevin Hao
[ Upstream commit e5c6b312ce3cc97e90ea159446e6bfa06645364d ] The struct sugov_tunables is protected by the kobject, so we can't free it directly. Otherwise we would get a call trace like this: ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x30 WARNING: CPU: 3 PID: 720 at lib/debugobjects.c:505 debug_print_object+0xb8/0x100 Modules linked in: CPU: 3 PID: 720 Comm: a.sh Tainted: G W 5.14.0-rc1-next-20210715-yocto-standard+ #507 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 40400009 (nZcv daif +PAN -UAO -TCO BTYPE=--) pc : debug_print_object+0xb8/0x100 lr : debug_print_object+0xb8/0x100 sp : ffff80001ecaf910 x29: ffff80001ecaf910 x28: ffff00011b10b8d0 x27: ffff800011043d80 x26: ffff00011a8f0000 x25: ffff800013cb3ff0 x24: 0000000000000000 x23: ffff80001142aa68 x22: ffff800011043d80 x21: ffff00010de46f20 x20: ffff800013c0c520 x19: ffff800011d8f5b0 x18: 0000000000000010 x17: 6e6968207473696c x16: 5f72656d6974203a x15: 6570797420746365 x14: 6a626f2029302065 x13: 303378302f307830 x12: 2b6e665f72656d69 x11: ffff8000124b1560 x10: ffff800012331520 x9 : ffff8000100ca6b0 x8 : 000000000017ffe8 x7 : c0000000fffeffff x6 : 0000000000000001 x5 : ffff800011d8c000 x4 : ffff800011d8c740 x3 : 0000000000000000 x2 : ffff0001108301c0 x1 : ab3c90eedf9c0f00 x0 : 0000000000000000 Call trace: debug_print_object+0xb8/0x100 __debug_check_no_obj_freed+0x1c0/0x230 debug_check_no_obj_freed+0x20/0x88 slab_free_freelist_hook+0x154/0x1c8 kfree+0x114/0x5d0 sugov_exit+0xbc/0xc0 cpufreq_exit_governor+0x44/0x90 cpufreq_set_policy+0x268/0x4a8 store_scaling_governor+0xe0/0x128 store+0xc0/0xf0 sysfs_kf_write+0x54/0x80 kernfs_fop_write_iter+0x128/0x1c0 new_sync_write+0xf0/0x190 vfs_write+0x2d4/0x478 ksys_write+0x74/0x100 __arm64_sys_write+0x24/0x30 invoke_syscall.constprop.0+0x54/0xe0 do_el0_svc+0x64/0x158 el0_svc+0x2c/0xb0 el0t_64_sync_handler+0xb0/0xb8 el0t_64_sync+0x198/0x19c irq event stamp: 5518 hardirqs last enabled at (5517): [<ffff8000100cbd7c>] console_unlock+0x554/0x6c8 hardirqs last disabled at (5518): [<ffff800010fc0638>] el1_dbg+0x28/0xa0 softirqs last enabled at (5504): [<ffff8000100106e0>] __do_softirq+0x4d0/0x6c0 softirqs last disabled at (5483): [<ffff800010049548>] irq_exit+0x1b0/0x1b8 So split the original sugov_tunables_free() into two functions, sugov_clear_global_tunables() is just used to clear the global_tunables and the new sugov_tunables_free() is used as kobj_type::release to release the sugov_tunables safely. Fixes: 9bdcb44e391d ("cpufreq: schedutil: New governor based on scheduler utilization data") Cc: 4.7+ <stable@vger.kernel.org> # 4.7+ Signed-off-by: Kevin Hao <haokexin@gmail.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-09-26sched/idle: Make the idle timer expire in hard interrupt contextSebastian Andrzej Siewior
[ Upstream commit 9848417926353daa59d2b05eb26e185063dbac6e ] The intel powerclamp driver will setup a per-CPU worker with RT priority. The worker will then invoke play_idle() in which it remains in the idle poll loop until it is stopped by the timer it started earlier. That timer needs to expire in hard interrupt context on PREEMPT_RT. Otherwise the timer will expire in ksoftirqd as a SOFT timer but that task won't be scheduled on the CPU because its priority is lower than the priority of the worker which is in the idle loop. Always expire the idle timer in hard interrupt context. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210906113034.jgfxrjdvxnjqgtmc@linutronix.de Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-09-15sched: Fix UCLAMP_FLAG_IDLE settingQuentin Perret
[ Upstream commit ca4984a7dd863f3e1c0df775ae3e744bff24c303 ] The UCLAMP_FLAG_IDLE flag is set on a runqueue when dequeueing the last uclamp active task (that is, when buckets.tasks reaches 0 for all buckets) to maintain the last uclamp.max and prevent blocked util from suddenly becoming visible. However, there is an asymmetry in how the flag is set and cleared which can lead to having the flag set whilst there are active tasks on the rq. Specifically, the flag is cleared in the uclamp_rq_inc() path, which is called at enqueue time, but set in uclamp_rq_dec_id() which is called both when dequeueing a task _and_ in the update_uclamp_active() path. As a result, when both uclamp_rq_{dec,ind}_id() are called from update_uclamp_active(), the flag ends up being set but not cleared, hence leaving the runqueue in a broken state. Fix this by clearing the flag in update_uclamp_active() as well. Fixes: e496187da710 ("sched/uclamp: Enforce last task's UCLAMP_MAX") Reported-by: Rick Yiu <rickyiu@google.com> Signed-off-by: Quentin Perret <qperret@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Qais Yousef <qais.yousef@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20210805102154.590709-2-qperret@google.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-09-15sched/numa: Fix is_core_idle()Mika Penttilä
[ Upstream commit 1c6829cfd3d5124b125e6df41158665aea413b35 ] Use the loop variable instead of the function argument to test the other SMT siblings for idle. Fixes: ff7db0bf24db ("sched/numa: Prefer using an idle CPU as a migration target instead of comparing tasks") Signed-off-by: Mika Penttilä <mika.penttila@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Pankaj Gupta <pankaj.gupta@ionos.com> Link: https://lkml.kernel.org/r/20210722063946.28951-1-mika.penttila@gmail.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-09-15sched/deadline: Fix missing clock update in migrate_task_rq_dl()Dietmar Eggemann
[ Upstream commit b4da13aa28d4fd0071247b7b41c579ee8a86c81a ] A missing clock update is causing the following warning: rq->clock_update_flags < RQCF_ACT_SKIP WARNING: CPU: 112 PID: 2041 at kernel/sched/sched.h:1453 sub_running_bw.isra.0+0x190/0x1a0 ... CPU: 112 PID: 2041 Comm: sugov:112 Tainted: G W 5.14.0-rc1 #1 Hardware name: WIWYNN Mt.Jade Server System B81.030Z1.0007/Mt.Jade Motherboard, BIOS 1.6.20210526 (SCP: 1.06.20210526) 2021/05/26 ... Call trace: sub_running_bw.isra.0+0x190/0x1a0 migrate_task_rq_dl+0xf8/0x1e0 set_task_cpu+0xa8/0x1f0 try_to_wake_up+0x150/0x3d4 wake_up_q+0x64/0xc0 __up_write+0xd0/0x1c0 up_write+0x4c/0x2b0 cppc_set_perf+0x120/0x2d0 cppc_cpufreq_set_target+0xe0/0x1a4 [cppc_cpufreq] __cpufreq_driver_target+0x74/0x140 sugov_work+0x64/0x80 kthread_worker_fn+0xe0/0x230 kthread+0x138/0x140 ret_from_fork+0x10/0x18 The task causing this is the `cppc_fie` DL task introduced by commit 1eb5dde674f5 ("cpufreq: CPPC: Add support for frequency invariance"). With CONFIG_ACPI_CPPC_CPUFREQ_FIE=y and schedutil cpufreq governor on slow-switching system (like on this Ampere Altra WIWYNN Mt. Jade Arm Server): DL task `curr=sugov:112` lets `p=cppc_fie` migrate and since the latter is in `non_contending` state, migrate_task_rq_dl() calls sub_running_bw()->__sub_running_bw()->cpufreq_update_util()-> rq_clock()->assert_clock_updated() on p. Fix this by updating the clock for a non_contending task in migrate_task_rq_dl() before calling sub_running_bw(). Reported-by: Bruno Goncalves <bgoncalv@redhat.com> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Daniel Bristot de Oliveira <bristot@kernel.org> Acked-by: Juri Lelli <juri.lelli@redhat.com> Link: https://lore.kernel.org/r/20210804135925.3734605-1-dietmar.eggemann@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-09-15sched/deadline: Fix reset_on_fork reporting of DL tasksQuentin Perret
[ Upstream commit f95091536f78971b269ec321b057b8d630b0ad8a ] It is possible for sched_getattr() to incorrectly report the state of the reset_on_fork flag when called on a deadline task. Indeed, if the flag was set on a deadline task using sched_setattr() with flags (SCHED_FLAG_RESET_ON_FORK | SCHED_FLAG_KEEP_PARAMS), then p->sched_reset_on_fork will be set, but __setscheduler() will bail out early, which means that the dl_se->flags will not get updated by __setscheduler_params()->__setparam_dl(). Consequently, if sched_getattr() is then called on the task, __getparam_dl() will override kattr.sched_flags with the now out-of-date copy in dl_se->flags and report the stale value to userspace. To fix this, make sure to only copy the flags that are relevant to sched_deadline to and from the dl_se->flags field. Signed-off-by: Quentin Perret <qperret@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20210727101103.2729607-2-qperret@google.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-09-03kthread: Fix PF_KTHREAD vs to_kthread() racePeter Zijlstra
commit 3a7956e25e1d7b3c148569e78895e1f3178122a9 upstream. The kthread_is_per_cpu() construct relies on only being called on PF_KTHREAD tasks (per the WARN in to_kthread). This gives rise to the following usage pattern: if ((p->flags & PF_KTHREAD) && kthread_is_per_cpu(p)) However, as reported by syzcaller, this is broken. The scenario is: CPU0 CPU1 (running p) (p->flags & PF_KTHREAD) // true begin_new_exec() me->flags &= ~(PF_KTHREAD|...); kthread_is_per_cpu(p) to_kthread(p) WARN(!(p->flags & PF_KTHREAD) <-- *SPLAT* Introduce __to_kthread() that omits the WARN and is sure to check both values. Use this to remove the problematic pattern for kthread_is_per_cpu() and fix a number of other kthread_*() functions that have similar issues but are currently not used in ways that would expose the problem. Notably kthread_func() is only ever called on 'current', while kthread_probe_data() is only used for PF_WQ_WORKER, which implies the task is from kthread_create*(). Fixes: ac687e6e8c26 ("kthread: Extract KTHREAD_IS_PER_CPU") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com> Link: https://lkml.kernel.org/r/YH6WJc825C4P0FCK@hirez.programming.kicks-ass.net [ Drop the balance_push() hunk as it is not needed. ] Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-08-12sched/rt: Fix double enqueue caused by rt_effective_prioPeter Zijlstra
commit f558c2b834ec27e75d37b1c860c139e7b7c3a8e4 upstream. Double enqueues in rt runqueues (list) have been reported while running a simple test that spawns a number of threads doing a short sleep/run pattern while being concurrently setscheduled between rt and fair class. WARNING: CPU: 3 PID: 2825 at kernel/sched/rt.c:1294 enqueue_task_rt+0x355/0x360 CPU: 3 PID: 2825 Comm: setsched__13 RIP: 0010:enqueue_task_rt+0x355/0x360 Call Trace: __sched_setscheduler+0x581/0x9d0 _sched_setscheduler+0x63/0xa0 do_sched_setscheduler+0xa0/0x150 __x64_sys_sched_setscheduler+0x1a/0x30 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae list_add double add: new=ffff9867cb629b40, prev=ffff9867cb629b40, next=ffff98679fc67ca0. kernel BUG at lib/list_debug.c:31! invalid opcode: 0000 [#1] PREEMPT_RT SMP PTI CPU: 3 PID: 2825 Comm: setsched__13 RIP: 0010:__list_add_valid+0x41/0x50 Call Trace: enqueue_task_rt+0x291/0x360 __sched_setscheduler+0x581/0x9d0 _sched_setscheduler+0x63/0xa0 do_sched_setscheduler+0xa0/0x150 __x64_sys_sched_setscheduler+0x1a/0x30 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae __sched_setscheduler() uses rt_effective_prio() to handle proper queuing of priority boosted tasks that are setscheduled while being boosted. rt_effective_prio() is however called twice per each __sched_setscheduler() call: first directly by __sched_setscheduler() before dequeuing the task and then by __setscheduler() to actually do the priority change. If the priority of the pi_top_task is concurrently being changed however, it might happen that the two calls return different results. If, for example, the first call returned the same rt priority the task was running at and the second one a fair priority, the task won't be removed by the rt list (on_list still set) and then enqueued in the fair runqueue. When eventually setscheduled back to rt it will be seen as enqueued already and the WARNING/BUG be issued. Fix this by calling rt_effective_prio() only once and then reusing the return value. While at it refactor code as well for clarity. Concurrent priority inheritance handling is still safe and will eventually converge to a new state by following the inheritance chain(s). Fixes: 0782e63bc6fe ("sched: Handle priority boosted tasks proper in setscheduler()") [squashed Peterz changes; added changelog] Reported-by: Mark Simmons <msimmons@redhat.com> Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210803104501.38333-1-juri.lelli@redhat.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-25sched/fair: Fix CFS bandwidth hrtimer expiry typeOdin Ugedal
[ Upstream commit 72d0ad7cb5bad265adb2014dbe46c4ccb11afaba ] The time remaining until expiry of the refresh_timer can be negative. Casting the type to an unsigned 64-bit value will cause integer underflow, making the runtime_refresh_within return false instead of true. These situations are rare, but they do happen. This does not cause user-facing issues or errors; other than possibly unthrottling cfs_rq's using runtime from the previous period(s), making the CFS bandwidth enforcement less strict in those (special) situations. Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ben Segall <bsegall@google.com> Link: https://lore.kernel.org/r/20210629121452.18429-1-odin@uged.al Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-20sched/uclamp: Ignore max aggregation if rq is idleXuewen Yan
[ Upstream commit 3e1493f46390618ea78607cb30c58fc19e2a5035 ] When a task wakes up on an idle rq, uclamp_rq_util_with() would max aggregate with rq value. But since there is no task enqueued yet, the values are stale based on the last task that was running. When the new task actually wakes up and enqueued, then the rq uclamp values should reflect that of the newly woken up task effective uclamp values. This is a problem particularly for uclamp_max because it default to 1024. If a task p with uclamp_max = 512 wakes up, then max aggregation would ignore the capping that should apply when this task is enqueued, which is wrong. Fix that by ignoring max aggregation if the rq is idle since in that case the effective uclamp value of the rq will be the ones of the task that will wake up. Fixes: 9d20ad7dfc9a ("sched/uclamp: Add uclamp_util_with()") Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> [qias: Changelog] Reviewed-by: Qais Yousef <qais.yousef@arm.com> Link: https://lore.kernel.org/r/20210630141204.8197-1-xuewen.yan94@gmail.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-19rq-qos: fix missed wake-ups in rq_qos_throttle try twoJan Kara
commit 11c7aa0ddea8611007768d3e6b58d45dc60a19e1 upstream. Commit 545fbd0775ba ("rq-qos: fix missed wake-ups in rq_qos_throttle") tried to fix a problem that a process could be sleeping in rq_qos_wait() without anyone to wake it up. However the fix is not complete and the following can still happen: CPU1 (waiter1) CPU2 (waiter2) CPU3 (waker) rq_qos_wait() rq_qos_wait() acquire_inflight_cb() -> fails acquire_inflight_cb() -> fails completes IOs, inflight decreased prepare_to_wait_exclusive() prepare_to_wait_exclusive() has_sleeper = !wq_has_single_sleeper() -> true as there are two sleepers has_sleeper = !wq_has_single_sleeper() -> true io_schedule() io_schedule() Deadlock as now there's nobody to wakeup the two waiters. The logic automatically blocking when there are already sleepers is really subtle and the only way to make it work reliably is that we check whether there are some waiters in the queue when adding ourselves there. That way, we are guaranteed that at least the first process to enter the wait queue will recheck the waiting condition before going to sleep and thus guarantee forward progress. Fixes: 545fbd0775ba ("rq-qos: fix missed wake-ups in rq_qos_throttle") CC: stable@vger.kernel.org Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20210607112613.25344-1-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-19sched/fair: Ensure _sum and _avg values stay consistentOdin Ugedal
[ Upstream commit 1c35b07e6d3986474e5635be566e7bc79d97c64d ] The _sum and _avg values are in general sync together with the PELT divider. They are however not always completely in perfect sync, resulting in situations where _sum gets to zero while _avg stays positive. Such situations are undesirable. This comes from the fact that PELT will increase period_contrib, also increasing the PELT divider, without updating _sum and _avg values to stay in perfect sync where (_sum == _avg * divider). However, such PELT change will never lower _sum, making it impossible to end up in a situation where _sum is zero and _avg is not. Therefore, we need to ensure that when subtracting load outside PELT, that when _sum is zero, _avg is also set to zero. This occurs when (_sum < _avg * divider), and the subtracted (_avg * divider) is bigger or equal to the current _sum, while the subtracted _avg is smaller than the current _avg. Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Link: https://lore.kernel.org/r/20210624111815.57937-1-odin@uged.al Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14psi: Fix race between psi_trigger_create/destroyZhaoyang Huang
[ Upstream commit 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83 ] Race detected between psi_trigger_destroy/create as shown below, which cause panic by accessing invalid psi_system->poll_wait->wait_queue_entry and psi_system->poll_timer->entry->next. Under this modification, the race window is removed by initialising poll_wait and poll_timer in group_init which are executed only once at beginning. psi_trigger_destroy() psi_trigger_create() mutex_lock(trigger_lock); rcu_assign_pointer(poll_task, NULL); mutex_unlock(trigger_lock); mutex_lock(trigger_lock); if (!rcu_access_pointer(group->poll_task)) { timer_setup(poll_timer, poll_timer_fn, 0); rcu_assign_pointer(poll_task, task); } mutex_unlock(trigger_lock); synchronize_rcu(); del_timer_sync(poll_timer); <-- poll_timer has been reinitialized by psi_trigger_create() So, trigger_lock/RCU correctly protects destruction of group->poll_task but misses this race affecting poll_timer and poll_wait. Fixes: 461daba06bdc ("psi: eliminate kthread_worker from psi trigger scheduling mechanism") Co-developed-by: ziwei.dai <ziwei.dai@unisoc.com> Signed-off-by: ziwei.dai <ziwei.dai@unisoc.com> Co-developed-by: ke.wang <ke.wang@unisoc.com> Signed-off-by: ke.wang <ke.wang@unisoc.com> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Link: https://lkml.kernel.org/r/1623371374-15664-1-git-send-email-huangzhaoyang@gmail.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14sched/uclamp: Fix uclamp_tg_restrict()Qais Yousef
[ Upstream commit 0213b7083e81f4acd69db32cb72eb4e5f220329a ] Now cpu.uclamp.min acts as a protection, we need to make sure that the uclamp request of the task is within the allowed range of the cgroup, that is it is clamp()'ed correctly by tg->uclamp[UCLAMP_MIN] and tg->uclamp[UCLAMP_MAX]. As reported by Xuewen [1] we can have some corner cases where there's inversion between uclamp requested by task (p) and the uclamp values of the taskgroup it's attached to (tg). Following table demonstrates 2 corner cases: | p | tg | effective -----------+-----+------+----------- CASE 1 -----------+-----+------+----------- uclamp_min | 60% | 0% | 60% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- CASE 2 -----------+-----+------+----------- uclamp_min | 0% | 30% | 30% -----------+-----+------+----------- uclamp_max | 20% | 50% | 20% -----------+-----+------+----------- With this fix we get: | p | tg | effective -----------+-----+------+----------- CASE 1 -----------+-----+------+----------- uclamp_min | 60% | 0% | 50% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- CASE 2 -----------+-----+------+----------- uclamp_min | 0% | 30% | 30% -----------+-----+------+----------- uclamp_max | 20% | 50% | 30% -----------+-----+------+----------- Additionally uclamp_update_active_tasks() must now unconditionally update both UCLAMP_MIN/MAX because changing the tg's UCLAMP_MAX for instance could have an impact on the effective UCLAMP_MIN of the tasks. | p | tg | effective -----------+-----+------+----------- old -----------+-----+------+----------- uclamp_min | 60% | 0% | 50% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- *new* -----------+-----+------+----------- uclamp_min | 60% | 0% | *60%* -----------+-----+------+----------- uclamp_max | 80% |*70%* | *70%* -----------+-----+------+----------- [1] https://lore.kernel.org/lkml/CAB8ipk_a6VFNjiEnHRHkUMBKbA+qzPQvhtNjJ_YNzQhqV_o8Zw@mail.gmail.com/ Fixes: 0c18f2ecfcc2 ("sched/uclamp: Fix wrong implementation of cpu.uclamp.min") Reported-by: Xuewen Yan <xuewen.yan94@gmail.com> Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210617165155.3774110-1-qais.yousef@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14sched/rt: Fix Deadline utilization tracking during policy changeVincent Donnefort
[ Upstream commit d7d607096ae6d378b4e92d49946d22739c047d4c ] DL keeps track of the utilization on a per-rq basis with the structure avg_dl. This utilization is updated during task_tick_dl(), put_prev_task_dl() and set_next_task_dl(). However, when the current running task changes its policy, set_next_task_dl() which would usually take care of updating the utilization when the rq starts running DL tasks, will not see a such change, leaving the avg_dl structure outdated. When that very same task will be dequeued later, put_prev_task_dl() will then update the utilization, based on a wrong last_update_time, leading to a huge spike in the DL utilization signal. The signal would eventually recover from this issue after few ms. Even if no DL tasks are run, avg_dl is also updated in __update_blocked_others(). But as the CPU capacity depends partly on the avg_dl, this issue has nonetheless a significant impact on the scheduler. Fix this issue by ensuring a load update when a running task changes its policy to DL. Fixes: 3727e0e ("sched/dl: Add dl_rq utilization tracking") Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/1624271872-211872-3-git-send-email-vincent.donnefort@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14sched/rt: Fix RT utilization tracking during policy changeVincent Donnefort
[ Upstream commit fecfcbc288e9f4923f40fd23ca78a6acdc7fdf6c ] RT keeps track of the utilization on a per-rq basis with the structure avg_rt. This utilization is updated during task_tick_rt(), put_prev_task_rt() and set_next_task_rt(). However, when the current running task changes its policy, set_next_task_rt() which would usually take care of updating the utilization when the rq starts running RT tasks, will not see a such change, leaving the avg_rt structure outdated. When that very same task will be dequeued later, put_prev_task_rt() will then update the utilization, based on a wrong last_update_time, leading to a huge spike in the RT utilization signal. The signal would eventually recover from this issue after few ms. Even if no RT tasks are run, avg_rt is also updated in __update_blocked_others(). But as the CPU capacity depends partly on the avg_rt, this issue has nonetheless a significant impact on the scheduler. Fix this issue by ensuring a load update when a running task changes its policy to RT. Fixes: 371bf427 ("sched/rt: Add rt_rq utilization tracking") Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/1624271872-211872-2-git-send-email-vincent.donnefort@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14sched/uclamp: Fix locking around cpu_util_update_eff()Qais Yousef
[ Upstream commit 93b73858701fd01de26a4a874eb95f9b7156fd4b ] cpu_cgroup_css_online() calls cpu_util_update_eff() without holding the uclamp_mutex or rcu_read_lock() like other call sites, which is a mistake. The uclamp_mutex is required to protect against concurrent reads and writes that could update the cgroup hierarchy. The rcu_read_lock() is required to traverse the cgroup data structures in cpu_util_update_eff(). Surround the caller with the required locks and add some asserts to better document the dependency in cpu_util_update_eff(). Fixes: 7226017ad37a ("sched/uclamp: Fix a bug in propagating uclamp value in new cgroups") Reported-by: Quentin Perret <qperret@google.com> Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210510145032.1934078-3-qais.yousef@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14sched/uclamp: Fix wrong implementation of cpu.uclamp.minQais Yousef
[ Upstream commit 0c18f2ecfcc274a4bcc1d122f79ebd4001c3b445 ] cpu.uclamp.min is a protection as described in cgroup-v2 Resource Distribution Model Documentation/admin-guide/cgroup-v2.rst which means we try our best to preserve the minimum performance point of tasks in this group. See full description of cpu.uclamp.min in the cgroup-v2.rst. But the current implementation makes it a limit, which is not what was intended. For example: tg->cpu.uclamp.min = 20% p0->uclamp[UCLAMP_MIN] = 0 p1->uclamp[UCLAMP_MIN] = 50% Previous Behavior (limit): p0->effective_uclamp = 0 p1->effective_uclamp = 20% New Behavior (Protection): p0->effective_uclamp = 20% p1->effective_uclamp = 50% Which is inline with how protections should work. With this change the cgroup and per-task behaviors are the same, as expected. Additionally, we remove the confusing relationship between cgroup and !user_defined flag. We don't want for example RT tasks that are boosted by default to max to change their boost value when they attach to a cgroup. If a cgroup wants to limit the max performance point of tasks attached to it, then cpu.uclamp.max must be set accordingly. Or if they want to set different boost value based on cgroup, then sysctl_sched_util_clamp_min_rt_default must be used to NOT boost to max and set the right cpu.uclamp.min for each group to let the RT tasks obtain the desired boost value when attached to that group. As it stands the dependency on !user_defined flag adds an extra layer of complexity that is not required now cpu.uclamp.min behaves properly as a protection. The propagation model of effective cpu.uclamp.min in child cgroups as implemented by cpu_util_update_eff() is still correct. The parent protection sets an upper limit of what the child cgroups will effectively get. Fixes: 3eac870a3247 (sched/uclamp: Use TG's clamps to restrict TASK's clamps) Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210510145032.1934078-2-qais.yousef@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14sched/fair: Fix ascii art by relpacing tabsOdin Ugedal
[ Upstream commit 08f7c2f4d0e9f4283f5796b8168044c034a1bfcb ] When using something other than 8 spaces per tab, this ascii art makes not sense, and the reader might end up wondering what this advanced equation "is". Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lkml.kernel.org/r/20210518125202.78658-4-odin@uged.al Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14sched/core: Initialize the idle task with preemption disabledValentin Schneider
[ Upstream commit f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674 ] As pointed out by commit de9b8f5dcbd9 ("sched: Fix crash trying to dequeue/enqueue the idle thread") init_idle() can and will be invoked more than once on the same idle task. At boot time, it is invoked for the boot CPU thread by sched_init(). Then smp_init() creates the threads for all the secondary CPUs and invokes init_idle() on them. As the hotplug machinery brings the secondaries to life, it will issue calls to idle_thread_get(), which itself invokes init_idle() yet again. In this case it's invoked twice more per secondary: at _cpu_up(), and at bringup_cpu(). Given smp_init() already initializes the idle tasks for all *possible* CPUs, no further initialization should be required. Now, removing init_idle() from idle_thread_get() exposes some interesting expectations with regards to the idle task's preempt_count: the secondary startup always issues a preempt_disable(), requiring some reset of the preempt count to 0 between hot-unplug and hotplug, which is currently served by idle_thread_get() -> idle_init(). Given the idle task is supposed to have preemption disabled once and never see it re-enabled, it seems that what we actually want is to initialize its preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove init_idle() from idle_thread_get(). Secondary startups were patched via coccinelle: @begone@ @@ -preempt_disable(); ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-06-23sched/pelt: Ensure that *_sum is always synced with *_avgVincent Guittot
[ Upstream commit fcf6631f3736985ec89bdd76392d3c7bfb60119f ] Rounding in PELT calculation happening when entities are attached/detached of a cfs_rq can result into situations where util/runnable_avg is not null but util/runnable_sum is. This is normally not possible so we need to ensure that util/runnable_sum stays synced with util/runnable_avg. detach_entity_load_avg() is the last place where we don't sync util/runnable_sum with util/runnbale_avg when moving some sched_entities Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210601085832.12626-1-vincent.guittot@linaro.org Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-06-16sched/fair: Fix util_est UTIL_AVG_UNCHANGED handlingDietmar Eggemann
commit 68d7a190682aa4eb02db477328088ebad15acc83 upstream. The util_est internal UTIL_AVG_UNCHANGED flag which is used to prevent unnecessary util_est updates uses the LSB of util_est.enqueued. It is exposed via _task_util_est() (and task_util_est()). Commit 92a801e5d5b7 ("sched/fair: Mask UTIL_AVG_UNCHANGED usages") mentions that the LSB is lost for util_est resolution but find_energy_efficient_cpu() checks if task_util_est() returns 0 to return prev_cpu early. _task_util_est() returns the max value of util_est.ewma and util_est.enqueued or'ed w/ UTIL_AVG_UNCHANGED. So task_util_est() returning the max of task_util() and _task_util_est() will never return 0 under the default SCHED_FEAT(UTIL_EST, true). To fix this use the MSB of util_est.enqueued instead and keep the flag util_est internal, i.e. don't export it via _task_util_est(). The maximal possible util_avg value for a task is 1024 so the MSB of 'unsigned int util_est.enqueued' isn't used to store a util value. As a caveat the code behind the util_est_se trace point has to filter UTIL_AVG_UNCHANGED to see the real util_est.enqueued value which should be easy to do. This also fixes an issue report by Xuewen Yan that util_est_update() only used UTIL_AVG_UNCHANGED for the subtrahend of the equation: last_enqueued_diff = ue.enqueued - (task_util() | UTIL_AVG_UNCHANGED) Fixes: b89997aa88f0b sched/pelt: Fix task util_est update filtering Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Xuewen Yan <xuewen.yan@unisoc.com> Reviewed-by: Vincent Donnefort <vincent.donnefort@arm.com> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20210602145808.1562603-1-dietmar.eggemann@arm.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-06-16sched/fair: Make sure to update tg contrib for blocked loadVincent Guittot
commit 02da26ad5ed6ea8680e5d01f20661439611ed776 upstream. During the update of fair blocked load (__update_blocked_fair()), we update the contribution of the cfs in tg->load_avg if cfs_rq's pelt has decayed. Nevertheless, the pelt values of a cfs_rq could have been recently updated while propagating the change of a child. In this case, cfs_rq's pelt will not decayed because it has already been updated and we don't update tg->load_avg. __update_blocked_fair ... for_each_leaf_cfs_rq_safe: child cfs_rq update cfs_rq_load_avg() for child cfs_rq ... update_load_avg(cfs_rq_of(se), se, 0) ... update cfs_rq_load_avg() for parent cfs_rq -propagation of child's load makes parent cfs_rq->load_sum becoming null -UPDATE_TG is not set so it doesn't update parent cfs_rq->tg_load_avg_contrib .. for_each_leaf_cfs_rq_safe: parent cfs_rq update cfs_rq_load_avg() for parent cfs_rq - nothing to do because parent cfs_rq has already been updated recently so cfs_rq->tg_load_avg_contrib is not updated ... parent cfs_rq is decayed list_del_leaf_cfs_rq parent cfs_rq - but it still contibutes to tg->load_avg we must set UPDATE_TG flags when propagting pending load to the parent Fixes: 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path") Reported-by: Odin Ugedal <odin@uged.al> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Odin Ugedal <odin@uged.al> Link: https://lkml.kernel.org/r/20210527122916.27683-3-vincent.guittot@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-06-16sched/fair: Keep load_avg and load_sum syncedVincent Guittot
commit 7c7ad626d9a0ff0a36c1e2a3cfbbc6a13828d5eb upstream. when removing a cfs_rq from the list we only check _sum value so we must ensure that _avg and _sum stay synced so load_sum can't be null whereas load_avg is not after propagating load in the cgroup hierarchy. Use load_avg to compute load_sum similarly to what is done for util_sum and runnable_sum. Fixes: 0e2d2aaaae52 ("sched/fair: Rewrite PELT migration propagation") Reported-by: Odin Ugedal <odin@uged.al> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Odin Ugedal <odin@uged.al> Link: https://lkml.kernel.org/r/20210527122916.27683-2-vincent.guittot@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-05-19sched/fair: Fix unfairness caused by missing load decayOdin Ugedal
[ Upstream commit 0258bdfaff5bd13c4d2383150b7097aecd6b6d82 ] This fixes an issue where old load on a cfs_rq is not properly decayed, resulting in strange behavior where fairness can decrease drastically. Real workloads with equally weighted control groups have ended up getting a respective 99% and 1%(!!) of cpu time. When an idle task is attached to a cfs_rq by attaching a pid to a cgroup, the old load of the task is attached to the new cfs_rq and sched_entity by attach_entity_cfs_rq. If the task is then moved to another cpu (and therefore cfs_rq) before being enqueued/woken up, the load will be moved to cfs_rq->removed from the sched_entity. Such a move will happen when enforcing a cpuset on the task (eg. via a cgroup) that force it to move. The load will however not be removed from the task_group itself, making it look like there is a constant load on that cfs_rq. This causes the vruntime of tasks on other sibling cfs_rq's to increase faster than they are supposed to; causing severe fairness issues. If no other task is started on the given cfs_rq, and due to the cpuset it would not happen, this load would never be properly unloaded. With this patch the load will be properly removed inside update_blocked_averages. This also applies to tasks moved to the fair scheduling class and moved to another cpu, and this path will also fix that. For fork, the entity is queued right away, so this problem does not affect that. This applies to cases where the new process is the first in the cfs_rq, issue introduced 3d30544f0212 ("sched/fair: Apply more PELT fixes"), and when there has previously been load on the cgroup but the cgroup was removed from the leaflist due to having null PELT load, indroduced in 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path"). For a simple cgroup hierarchy (as seen below) with two equally weighted groups, that in theory should get 50/50 of cpu time each, it often leads to a load of 60/40 or 70/30. parent/ cg-1/ cpu.weight: 100 cpuset.cpus: 1 cg-2/ cpu.weight: 100 cpuset.cpus: 1 If the hierarchy is deeper (as seen below), while keeping cg-1 and cg-2 equally weighted, they should still get a 50/50 balance of cpu time. This however sometimes results in a balance of 10/90 or 1/99(!!) between the task groups. $ ps u -C stress USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 18568 1.1 0.0 3684 100 pts/12 R+ 13:36 0:00 stress --cpu 1 root 18580 99.3 0.0 3684 100 pts/12 R+ 13:36 0:09 stress --cpu 1 parent/ cg-1/ cpu.weight: 100 sub-group/ cpu.weight: 1 cpuset.cpus: 1 cg-2/ cpu.weight: 100 sub-group/ cpu.weight: 10000 cpuset.cpus: 1 This can be reproduced by attaching an idle process to a cgroup and moving it to a given cpuset before it wakes up. The issue is evident in many (if not most) container runtimes, and has been reproduced with both crun and runc (and therefore docker and all its "derivatives"), and with both cgroup v1 and v2. Fixes: 3d30544f0212 ("sched/fair: Apply more PELT fixes") Fixes: 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path") Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lkml.kernel.org/r/20210501141950.23622-2-odin@uged.al Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-05-19sched: Fix out-of-bound access in uclampQuentin Perret
[ Upstream commit 6d2f8909a5fabb73fe2a63918117943986c39b6c ] Util-clamp places tasks in different buckets based on their clamp values for performance reasons. However, the size of buckets is currently computed using a rounding division, which can lead to an off-by-one error in some configurations. For instance, with 20 buckets, the bucket size will be 1024/20=51. A task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly, correct indexes are in range [0,19], hence leading to an out of bound memory access. Clamp the bucket id to fix the issue. Fixes: 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting") Suggested-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Quentin Perret <qperret@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lkml.kernel.org/r/20210430151412.160913-1-qperret@google.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-05-14smp: Fix smp_call_function_single_async prototypeArnd Bergmann
commit 1139aeb1c521eb4a050920ce6c64c36c4f2a3ab7 upstream. As of commit 966a967116e6 ("smp: Avoid using two cache lines for struct call_single_data"), the smp code prefers 32-byte aligned call_single_data objects for performance reasons, but the block layer includes an instance of this structure in the main 'struct request' that is more senstive to size than to performance here, see 4ccafe032005 ("block: unalign call_single_data in struct request"). The result is a violation of the calling conventions that clang correctly points out: block/blk-mq.c:630:39: warning: passing 8-byte aligned argument to 32-byte aligned parameter 2 of 'smp_call_function_single_async' may result in an unaligned pointer access [-Walign-mismatch] smp_call_function_single_async(cpu, &rq->csd); It does seem that the usage of the call_single_data without cache line alignment should still be allowed by the smp code, so just change the function prototype so it accepts both, but leave the default alignment unchanged for the other users. This seems better to me than adding a local hack to shut up an otherwise correct warning in the caller. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Jens Axboe <axboe@kernel.dk> Link: https://lkml.kernel.org/r/20210505211300.3174456-1-arnd@kernel.org [nc: Fix conflicts, modify rq_csd_init] Signed-off-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-05-14sched/debug: Fix cgroup_path[] serializationWaiman Long
[ Upstream commit ad789f84c9a145f8a18744c0387cec22ec51651e ] The handling of sysrq key can be activated by echoing the key to /proc/sysrq-trigger or via the magic key sequence typed into a terminal that is connected to the system in some way (serial, USB or other mean). In the former case, the handling is done in a user context. In the latter case, it is likely to be in an interrupt context. Currently in print_cpu() of kernel/sched/debug.c, sched_debug_lock is taken with interrupt disabled for the whole duration of the calls to print_*_stats() and print_rq() which could last for the quite some time if the information dump happens on the serial console. If the system has many cpus and the sched_debug_lock is somehow busy (e.g. parallel sysrq-t), the system may hit a hard lockup panic depending on the actually serial console implementation of the system. The purpose of sched_debug_lock is to serialize the use of the global cgroup_path[] buffer in print_cpu(). The rests of the printk calls don't need serialization from sched_debug_lock. Calling printk() with interrupt disabled can still be problematic if multiple instances are running. Allocating a stack buffer of PATH_MAX bytes is not feasible because of the limited size of the kernel stack. The solution implemented in this patch is to allow only one caller at a time to use the full size group_path[], while other simultaneous callers will have to use shorter stack buffers with the possibility of path name truncation. A "..." suffix will be printed if truncation may have happened. The cgroup path name is provided for informational purpose only, so occasional path name truncation should not be a big problem. Fixes: efe25c2c7b3a ("sched: Reinstate group names in /proc/sched_debug") Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210415195426.6677-1-longman@redhat.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-05-14sched/fair: Fix shift-out-of-bounds in load_balance()Valentin Schneider
[ Upstream commit 39a2a6eb5c9b66ea7c8055026303b3aa681b49a5 ] Syzbot reported a handful of occurrences where an sd->nr_balance_failed can grow to much higher values than one would expect. A successful load_balance() resets it to 0; a failed one increments it. Once it gets to sd->cache_nice_tries + 3, this *should* trigger an active balance, which will either set it to sd->cache_nice_tries+1 or reset it to 0. However, in case the to-be-active-balanced task is not allowed to run on env->dst_cpu, then the increment is done without any further modification. This could then be repeated ad nauseam, and would explain the absurdly high values reported by syzbot (86, 149). VincentG noted there is value in letting sd->cache_nice_tries grow, so the shift itself should be fixed. That means preventing: """ If the value of the right operand is negative or is greater than or equal to the width of the promoted left operand, the behavior is undefined. """ Thus we need to cap the shift exponent to BITS_PER_TYPE(typeof(lefthand)) - 1. I had a look around for other similar cases via coccinelle: @expr@ position pos; expression E1; expression E2; @@ ( E1 >> E2@pos | E1 >> E2@pos ) @cst depends on expr@ position pos; expression expr.E1; constant cst; @@ ( E1 >> cst@pos | E1 << cst@pos ) @script:python depends on !cst@ pos << expr.pos; exp << expr.E2; @@ # Dirty hack to ignore constexpr if exp.upper() != exp: coccilib.report.print_report(pos[0], "Possible UB shift here") The only other match in kernel/sched is rq_clock_thermal() which employs sched_thermal_decay_shift, and that exponent is already capped to 10, so that one is fine. Fixes: 5a7f55590467 ("sched/fair: Relax constraint on task's load during load balance") Reported-by: syzbot+d7581744d5fd27c9fbe1@syzkaller.appspotmail.com Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: http://lore.kernel.org/r/000000000000ffac1205b9a2112f@google.com Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-05-11sched,psi: Handle potential task count underflow bugs more gracefullyCharan Teja Reddy
[ Upstream commit 9d10a13d1e4c349b76f1c675a874a7f981d6d3b4 ] psi_group_cpu->tasks, represented by the unsigned int, stores the number of tasks that could be stalled on a psi resource(io/mem/cpu). Decrementing these counters at zero leads to wrapping which further leads to the psi_group_cpu->state_mask is being set with the respective pressure state. This could result into the unnecessary time sampling for the pressure state thus cause the spurious psi events. This can further lead to wrong actions being taken at the user land based on these psi events. Though psi_bug is set under these conditions but that just for debug purpose. Fix it by decrementing the ->tasks count only when it is non-zero. Signed-off-by: Charan Teja Reddy <charante@codeaurora.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Link: https://lkml.kernel.org/r/1618585336-37219-1-git-send-email-charante@codeaurora.org Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-05-11sched,fair: Alternative sched_slice()Peter Zijlstra
[ Upstream commit 0c2de3f054a59f15e01804b75a04355c48de628c ] The current sched_slice() seems to have issues; there's two possible things that could be improved: - the 'nr_running' used for __sched_period() is daft when cgroups are considered. Using the RQ wide h_nr_running seems like a much more consistent number. - (esp) cgroups can slice it real fine, which makes for easy over-scheduling, ensure min_gran is what the name says. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210412102001.611897312@infradead.org Signed-off-by: Sasha Levin <sashal@kernel.org>
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