diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup/cgroup.c | 1 | ||||
| -rw-r--r-- | kernel/cgroup/cpuset.c | 222 | ||||
| -rw-r--r-- | kernel/sched/isolation.c | 4 | ||||
| -rw-r--r-- | kernel/time/timer_migration.c | 4 |
4 files changed, 152 insertions, 79 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index c22cda7766d8..be1d71dda317 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -2608,6 +2608,7 @@ static void cgroup_migrate_add_task(struct task_struct *task, mgctx->tset.nr_tasks++; + css_set_skip_task_iters(cset, task); list_move_tail(&task->cg_list, &cset->mg_tasks); if (list_empty(&cset->mg_node)) list_add_tail(&cset->mg_node, diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 9faf34377a88..e200de7c60b6 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -62,6 +62,75 @@ static const char * const perr_strings[] = { }; /* + * CPUSET Locking Convention + * ------------------------- + * + * Below are the four global/local locks guarding cpuset structures in lock + * acquisition order: + * - cpuset_top_mutex + * - cpu_hotplug_lock (cpus_read_lock/cpus_write_lock) + * - cpuset_mutex + * - callback_lock (raw spinlock) + * + * As cpuset will now indirectly flush a number of different workqueues in + * housekeeping_update() to update housekeeping cpumasks when the set of + * isolated CPUs is going to be changed, it may be vulnerable to deadlock + * if we hold cpus_read_lock while calling into housekeeping_update(). + * + * The first cpuset_top_mutex will be held except when calling into + * cpuset_handle_hotplug() from the CPU hotplug code where cpus_write_lock + * and cpuset_mutex will be held instead. The main purpose of this mutex + * is to prevent regular cpuset control file write actions from interfering + * with the call to housekeeping_update(), though CPU hotplug operation can + * still happen in parallel. This mutex also provides protection for some + * internal variables. + * + * A task must hold all the remaining three locks to modify externally visible + * or used fields of cpusets, though some of the internally used cpuset fields + * and internal variables can be modified without holding callback_lock. If only + * reliable read access of the externally used fields are needed, a task can + * hold either cpuset_mutex or callback_lock which are exposed to other + * external subsystems. + * + * If a task holds cpu_hotplug_lock and cpuset_mutex, it blocks others, + * ensuring that it is the only task able to also acquire callback_lock and + * be able to modify cpusets. It can perform various checks on the cpuset + * structure first, knowing nothing will change. It can also allocate memory + * without holding callback_lock. While it is performing these checks, various + * callback routines can briefly acquire callback_lock to query cpusets. Once + * it is ready to make the changes, it takes callback_lock, blocking everyone + * else. + * + * Calls to the kernel memory allocator cannot be made while holding + * callback_lock which is a spinlock, as the memory allocator may sleep or + * call back into cpuset code and acquire callback_lock. + * + * Now, the task_struct fields mems_allowed and mempolicy may be changed + * by other task, we use alloc_lock in the task_struct fields to protect + * them. + * + * The cpuset_common_seq_show() handlers only hold callback_lock across + * small pieces of code, such as when reading out possibly multi-word + * cpumasks and nodemasks. + */ + +static DEFINE_MUTEX(cpuset_top_mutex); +static DEFINE_MUTEX(cpuset_mutex); + +/* + * File level internal variables below follow one of the following exclusion + * rules. + * + * RWCS: Read/write-able by holding either cpus_write_lock (and optionally + * cpuset_mutex) or both cpus_read_lock and cpuset_mutex. + * + * CSCB: Readable by holding either cpuset_mutex or callback_lock. Writable + * by holding both cpuset_mutex and callback_lock. + * + * T: Read/write-able by holding the cpuset_top_mutex. + */ + +/* * For local partitions, update to subpartitions_cpus & isolated_cpus is done * in update_parent_effective_cpumask(). For remote partitions, it is done in * the remote_partition_*() and remote_cpus_update() helpers. @@ -70,19 +139,22 @@ static const char * const perr_strings[] = { * Exclusive CPUs distributed out to local or remote sub-partitions of * top_cpuset */ -static cpumask_var_t subpartitions_cpus; +static cpumask_var_t subpartitions_cpus; /* RWCS */ + +/* + * Exclusive CPUs in isolated partitions (shown in cpuset.cpus.isolated) + */ +static cpumask_var_t isolated_cpus; /* CSCB */ /* - * Exclusive CPUs in isolated partitions + * Set if housekeeping cpumasks are to be updated. */ -static cpumask_var_t isolated_cpus; +static bool update_housekeeping; /* RWCS */ /* - * isolated_cpus updating flag (protected by cpuset_mutex) - * Set if isolated_cpus is going to be updated in the current - * cpuset_mutex crtical section. + * Copy of isolated_cpus to be passed to housekeeping_update() */ -static bool isolated_cpus_updating; +static cpumask_var_t isolated_hk_cpus; /* T */ /* * A flag to force sched domain rebuild at the end of an operation. @@ -98,7 +170,7 @@ static bool isolated_cpus_updating; * Note that update_relax_domain_level() in cpuset-v1.c can still call * rebuild_sched_domains_locked() directly without using this flag. */ -static bool force_sd_rebuild; +static bool force_sd_rebuild; /* RWCS */ /* * Partition root states: @@ -218,42 +290,6 @@ struct cpuset top_cpuset = { .partition_root_state = PRS_ROOT, }; -/* - * There are two global locks guarding cpuset structures - cpuset_mutex and - * callback_lock. The cpuset code uses only cpuset_mutex. Other kernel - * subsystems can use cpuset_lock()/cpuset_unlock() to prevent change to cpuset - * structures. Note that cpuset_mutex needs to be a mutex as it is used in - * paths that rely on priority inheritance (e.g. scheduler - on RT) for - * correctness. - * - * A task must hold both locks to modify cpusets. If a task holds - * cpuset_mutex, it blocks others, ensuring that it is the only task able to - * also acquire callback_lock and be able to modify cpusets. It can perform - * various checks on the cpuset structure first, knowing nothing will change. - * It can also allocate memory while just holding cpuset_mutex. While it is - * performing these checks, various callback routines can briefly acquire - * callback_lock to query cpusets. Once it is ready to make the changes, it - * takes callback_lock, blocking everyone else. - * - * Calls to the kernel memory allocator can not be made while holding - * callback_lock, as that would risk double tripping on callback_lock - * from one of the callbacks into the cpuset code from within - * __alloc_pages(). - * - * If a task is only holding callback_lock, then it has read-only - * access to cpusets. - * - * Now, the task_struct fields mems_allowed and mempolicy may be changed - * by other task, we use alloc_lock in the task_struct fields to protect - * them. - * - * The cpuset_common_seq_show() handlers only hold callback_lock across - * small pieces of code, such as when reading out possibly multi-word - * cpumasks and nodemasks. - */ - -static DEFINE_MUTEX(cpuset_mutex); - /** * cpuset_lock - Acquire the global cpuset mutex * @@ -283,6 +319,7 @@ void lockdep_assert_cpuset_lock_held(void) */ void cpuset_full_lock(void) { + mutex_lock(&cpuset_top_mutex); cpus_read_lock(); mutex_lock(&cpuset_mutex); } @@ -291,12 +328,14 @@ void cpuset_full_unlock(void) { mutex_unlock(&cpuset_mutex); cpus_read_unlock(); + mutex_unlock(&cpuset_top_mutex); } #ifdef CONFIG_LOCKDEP bool lockdep_is_cpuset_held(void) { - return lockdep_is_held(&cpuset_mutex); + return lockdep_is_held(&cpuset_mutex) || + lockdep_is_held(&cpuset_top_mutex); } #endif @@ -961,7 +1000,7 @@ void rebuild_sched_domains_locked(void) * offline CPUs, a warning is emitted and we return directly to * prevent the panic. */ - for (i = 0; i < ndoms; ++i) { + for (i = 0; doms && i < ndoms; i++) { if (WARN_ON_ONCE(!cpumask_subset(doms[i], cpu_active_mask))) return; } @@ -1161,12 +1200,18 @@ static void reset_partition_data(struct cpuset *cs) static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus) { WARN_ON_ONCE(old_prs == new_prs); - if (new_prs == PRS_ISOLATED) + lockdep_assert_held(&callback_lock); + lockdep_assert_held(&cpuset_mutex); + if (new_prs == PRS_ISOLATED) { + if (cpumask_subset(xcpus, isolated_cpus)) + return; cpumask_or(isolated_cpus, isolated_cpus, xcpus); - else + } else { + if (!cpumask_intersects(xcpus, isolated_cpus)) + return; cpumask_andnot(isolated_cpus, isolated_cpus, xcpus); - - isolated_cpus_updating = true; + } + update_housekeeping = true; } /* @@ -1219,8 +1264,8 @@ static void partition_xcpus_del(int old_prs, struct cpuset *parent, isolated_cpus_update(old_prs, parent->partition_root_state, xcpus); - cpumask_and(xcpus, xcpus, cpu_active_mask); cpumask_or(parent->effective_cpus, parent->effective_cpus, xcpus); + cpumask_and(parent->effective_cpus, parent->effective_cpus, cpu_active_mask); } /* @@ -1284,22 +1329,43 @@ static bool prstate_housekeeping_conflict(int prstate, struct cpumask *new_cpus) } /* - * update_isolation_cpumasks - Update external isolation related CPU masks + * update_hk_sched_domains - Update HK cpumasks & rebuild sched domains * - * The following external CPU masks will be updated if necessary: - * - workqueue unbound cpumask + * Update housekeeping cpumasks and rebuild sched domains if necessary. + * This should be called at the end of cpuset or hotplug actions. */ -static void update_isolation_cpumasks(void) +static void update_hk_sched_domains(void) { - int ret; - - if (!isolated_cpus_updating) - return; + if (update_housekeeping) { + /* Updating HK cpumasks implies rebuild sched domains */ + update_housekeeping = false; + force_sd_rebuild = true; + cpumask_copy(isolated_hk_cpus, isolated_cpus); - ret = housekeeping_update(isolated_cpus); - WARN_ON_ONCE(ret < 0); + /* + * housekeeping_update() is now called without holding + * cpus_read_lock and cpuset_mutex. Only cpuset_top_mutex + * is still being held for mutual exclusion. + */ + mutex_unlock(&cpuset_mutex); + cpus_read_unlock(); + WARN_ON_ONCE(housekeeping_update(isolated_hk_cpus)); + cpus_read_lock(); + mutex_lock(&cpuset_mutex); + } + /* force_sd_rebuild will be cleared in rebuild_sched_domains_locked() */ + if (force_sd_rebuild) + rebuild_sched_domains_locked(); +} - isolated_cpus_updating = false; +/* + * Work function to invoke update_hk_sched_domains() + */ +static void hk_sd_workfn(struct work_struct *work) +{ + cpuset_full_lock(); + update_hk_sched_domains(); + cpuset_full_unlock(); } /** @@ -1450,7 +1516,6 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs, cs->remote_partition = true; cpumask_copy(cs->effective_xcpus, tmp->new_cpus); spin_unlock_irq(&callback_lock); - update_isolation_cpumasks(); cpuset_force_rebuild(); cs->prs_err = 0; @@ -1495,7 +1560,6 @@ static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp) compute_excpus(cs, cs->effective_xcpus); reset_partition_data(cs); spin_unlock_irq(&callback_lock); - update_isolation_cpumasks(); cpuset_force_rebuild(); /* @@ -1566,7 +1630,6 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus, if (xcpus) cpumask_copy(cs->exclusive_cpus, xcpus); spin_unlock_irq(&callback_lock); - update_isolation_cpumasks(); if (adding || deleting) cpuset_force_rebuild(); @@ -1910,7 +1973,6 @@ write_error: partition_xcpus_add(new_prs, parent, tmp->delmask); spin_unlock_irq(&callback_lock); - update_isolation_cpumasks(); if ((old_prs != new_prs) && (cmd == partcmd_update)) update_partition_exclusive_flag(cs, new_prs); @@ -2155,7 +2217,7 @@ get_css: WARN_ON(!is_in_v2_mode() && !cpumask_equal(cp->cpus_allowed, cp->effective_cpus)); - cpuset_update_tasks_cpumask(cp, cp->effective_cpus); + cpuset_update_tasks_cpumask(cp, tmp->new_cpus); /* * On default hierarchy, inherit the CS_SCHED_LOAD_BALANCE @@ -2878,7 +2940,6 @@ out: else if (isolcpus_updated) isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus); spin_unlock_irq(&callback_lock); - update_isolation_cpumasks(); /* Force update if switching back to member & update effective_xcpus */ update_cpumasks_hier(cs, &tmpmask, !new_prs); @@ -3168,9 +3229,8 @@ ssize_t cpuset_write_resmask(struct kernfs_open_file *of, } free_cpuset(trialcs); - if (force_sd_rebuild) - rebuild_sched_domains_locked(); out_unlock: + update_hk_sched_domains(); cpuset_full_unlock(); if (of_cft(of)->private == FILE_MEMLIST) schedule_flush_migrate_mm(); @@ -3278,6 +3338,7 @@ static ssize_t cpuset_partition_write(struct kernfs_open_file *of, char *buf, cpuset_full_lock(); if (is_cpuset_online(cs)) retval = update_prstate(cs, val); + update_hk_sched_domains(); cpuset_full_unlock(); return retval ?: nbytes; } @@ -3452,6 +3513,7 @@ static void cpuset_css_killed(struct cgroup_subsys_state *css) /* Reset valid partition back to member */ if (is_partition_valid(cs)) update_prstate(cs, PRS_MEMBER); + update_hk_sched_domains(); cpuset_full_unlock(); } @@ -3607,6 +3669,7 @@ int __init cpuset_init(void) BUG_ON(!alloc_cpumask_var(&top_cpuset.exclusive_cpus, GFP_KERNEL)); BUG_ON(!zalloc_cpumask_var(&subpartitions_cpus, GFP_KERNEL)); BUG_ON(!zalloc_cpumask_var(&isolated_cpus, GFP_KERNEL)); + BUG_ON(!zalloc_cpumask_var(&isolated_hk_cpus, GFP_KERNEL)); cpumask_setall(top_cpuset.cpus_allowed); nodes_setall(top_cpuset.mems_allowed); @@ -3778,6 +3841,7 @@ unlock: */ static void cpuset_handle_hotplug(void) { + static DECLARE_WORK(hk_sd_work, hk_sd_workfn); static cpumask_t new_cpus; static nodemask_t new_mems; bool cpus_updated, mems_updated; @@ -3859,9 +3923,21 @@ static void cpuset_handle_hotplug(void) rcu_read_unlock(); } - /* rebuild sched domains if necessary */ - if (force_sd_rebuild) - rebuild_sched_domains_cpuslocked(); + + /* + * Queue a work to call housekeeping_update() & rebuild_sched_domains() + * There will be a slight delay before the HK_TYPE_DOMAIN housekeeping + * cpumask can correctly reflect what is in isolated_cpus. + * + * We rely on WORK_STRUCT_PENDING_BIT to not requeue a work item that + * is still pending. Before the pending bit is cleared, the work data + * is copied out and work item dequeued. So it is possible to queue + * the work again before the hk_sd_workfn() is invoked to process the + * previously queued work. Since hk_sd_workfn() doesn't use the work + * item at all, this is not a problem. + */ + if (update_housekeeping || force_sd_rebuild) + queue_work(system_unbound_wq, &hk_sd_work); free_tmpmasks(ptmp); } diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 3b725d39c06e..ef152d401fe2 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -123,8 +123,6 @@ int housekeeping_update(struct cpumask *isol_mask) struct cpumask *trial, *old = NULL; int err; - lockdep_assert_cpus_held(); - trial = kmalloc(cpumask_size(), GFP_KERNEL); if (!trial) return -ENOMEM; @@ -136,7 +134,7 @@ int housekeeping_update(struct cpumask *isol_mask) } if (!housekeeping.flags) - static_branch_enable_cpuslocked(&housekeeping_overridden); + static_branch_enable(&housekeeping_overridden); if (housekeeping.flags & HK_FLAG_DOMAIN) old = housekeeping_cpumask_dereference(HK_TYPE_DOMAIN); diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index c1ed0d5e8de6..155eeaea4113 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -1559,8 +1559,6 @@ int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_cpumask) cpumask_var_t cpumask __free(free_cpumask_var) = CPUMASK_VAR_NULL; int cpu; - lockdep_assert_cpus_held(); - if (!works) return -ENOMEM; if (!alloc_cpumask_var(&cpumask, GFP_KERNEL)) @@ -1570,6 +1568,7 @@ int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_cpumask) * First set previously isolated CPUs as available (unisolate). * This cpumask contains only CPUs that switched to available now. */ + guard(cpus_read_lock)(); cpumask_andnot(cpumask, cpu_online_mask, exclude_cpumask); cpumask_andnot(cpumask, cpumask, tmigr_available_cpumask); @@ -1626,7 +1625,6 @@ static int __init tmigr_init_isolation(void) cpumask_andnot(cpumask, cpu_possible_mask, housekeeping_cpumask(HK_TYPE_DOMAIN)); /* Protect against RCU torture hotplug testing */ - guard(cpus_read_lock)(); return tmigr_isolated_exclude_cpumask(cpumask); } late_initcall(tmigr_init_isolation); |