From c54bc0fc84214b203f7a0ebfd1bd308ce2abe920 Mon Sep 17 00:00:00 2001 From: Anna-Maria Behnsen Date: Tue, 5 Apr 2022 21:17:32 +0200 Subject: timers: Fix warning condition in __run_timers() When the timer base is empty, base::next_expiry is set to base::clk + NEXT_TIMER_MAX_DELTA and base::next_expiry_recalc is false. When no timer is queued until jiffies reaches base::next_expiry value, the warning for not finding any expired timer and base::next_expiry_recalc is false in __run_timers() triggers. To prevent triggering the warning in this valid scenario base::timers_pending needs to be added to the warning condition. Fixes: 31cd0e119d50 ("timers: Recalculate next timer interrupt only when necessary") Reported-by: Johannes Berg Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20220405191732.7438-3-anna-maria@linutronix.de --- kernel/time/timer.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'kernel/time/timer.c') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 85f1021ad459..9dd2a39cb3b0 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1722,11 +1722,14 @@ static inline void __run_timers(struct timer_base *base) time_after_eq(jiffies, base->next_expiry)) { levels = collect_expired_timers(base, heads); /* - * The only possible reason for not finding any expired - * timer at this clk is that all matching timers have been - * dequeued. + * The two possible reasons for not finding any expired + * timer at this clk are that all matching timers have been + * dequeued or no timer has been queued since + * base::next_expiry was set to base::clk + + * NEXT_TIMER_MAX_DELTA. */ - WARN_ON_ONCE(!levels && !base->next_expiry_recalc); + WARN_ON_ONCE(!levels && !base->next_expiry_recalc + && base->timers_pending); base->clk++; base->next_expiry = __next_timer_interrupt(base); -- cgit v1.2.3 From 2731aa7d65dbb31c6dad14347c37d522bb3bc7c6 Mon Sep 17 00:00:00 2001 From: Anna-Maria Behnsen Date: Tue, 5 Apr 2022 21:17:31 +0200 Subject: timers: Initialize base::next_expiry_recalc in timers_prepare_cpu() When base::next_expiry_recalc is not initialized to false during cpu bringup in HOTPLUG_CPU and is accidently true and no timer is queued in the meantime, the loop through the wheel to find __next_timer_interrupt() might be done for nothing. Therefore initialize base::next_expiry_recalc to false in timers_prepare_cpu(). Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20220405191732.7438-2-anna-maria@linutronix.de --- kernel/time/timer.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/time/timer.c') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 9dd2a39cb3b0..204d6cd83d0e 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1953,6 +1953,7 @@ int timers_prepare_cpu(unsigned int cpu) base = per_cpu_ptr(&timer_bases[b], cpu); base->clk = jiffies; base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA; + base->next_expiry_recalc = false; base->timers_pending = false; base->is_idle = false; } -- cgit v1.2.3 From a2026e44eff5d74a83d7ffee6325a007bef85385 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 4 Apr 2022 16:47:55 +0200 Subject: timers: Simplify calc_index() The level granularity round up of calc_index() does: (x + (1 << n)) >> n which is obviously equivalent to (x >> n) + 1 but compilers can't figure that out despite the fact that the input range is known to not cause an overflow. It's neither intuitive to read. Just write out the obvious. Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/87h778j46c.ffs@tglx --- kernel/time/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/time/timer.c') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 204d6cd83d0e..60aebf2b7f0a 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -502,7 +502,7 @@ static inline unsigned calc_index(unsigned long expires, unsigned lvl, * * Round up with level granularity to prevent this. */ - expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl); + expires = (expires >> LVL_SHIFT(lvl)) + 1; *bucket_expiry = expires << LVL_SHIFT(lvl); return LVL_OFFS(lvl) + (expires & LVL_MASK); } -- cgit v1.2.3 From efaa0227f6c6a5073951b20cf2f8c63c4155306c Mon Sep 17 00:00:00 2001 From: tangmeng Date: Tue, 15 Feb 2022 14:50:19 +0800 Subject: timers: Move timer sysctl into the timer code This is part of the effort to reduce kernel/sysctl.c to only contain the core logic. Signed-off-by: tangmeng Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220215065019.7520-1-tangmeng@uniontech.com --- kernel/time/timer.c | 53 ++++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 38 insertions(+), 15 deletions(-) (limited to 'kernel/time/timer.c') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 60aebf2b7f0a..ef082d43c307 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -44,6 +44,7 @@ #include #include #include +#include #include #include @@ -223,7 +224,7 @@ static void timer_update_keys(struct work_struct *work); static DECLARE_WORK(timer_update_work, timer_update_keys); #ifdef CONFIG_SMP -unsigned int sysctl_timer_migration = 1; +static unsigned int sysctl_timer_migration = 1; DEFINE_STATIC_KEY_FALSE(timers_migration_enabled); @@ -234,7 +235,42 @@ static void timers_update_migration(void) else static_branch_disable(&timers_migration_enabled); } -#else + +#ifdef CONFIG_SYSCTL +static int timer_migration_handler(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int ret; + + mutex_lock(&timer_keys_mutex); + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (!ret && write) + timers_update_migration(); + mutex_unlock(&timer_keys_mutex); + return ret; +} + +static struct ctl_table timer_sysctl[] = { + { + .procname = "timer_migration", + .data = &sysctl_timer_migration, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = timer_migration_handler, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + {} +}; + +static int __init timer_sysctl_init(void) +{ + register_sysctl("kernel", timer_sysctl); + return 0; +} +device_initcall(timer_sysctl_init); +#endif /* CONFIG_SYSCTL */ +#else /* CONFIG_SMP */ static inline void timers_update_migration(void) { } #endif /* !CONFIG_SMP */ @@ -251,19 +287,6 @@ void timers_update_nohz(void) schedule_work(&timer_update_work); } -int timer_migration_handler(struct ctl_table *table, int write, - void *buffer, size_t *lenp, loff_t *ppos) -{ - int ret; - - mutex_lock(&timer_keys_mutex); - ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); - if (!ret && write) - timers_update_migration(); - mutex_unlock(&timer_keys_mutex); - return ret; -} - static inline bool is_timers_nohz_active(void) { return static_branch_unlikely(&timers_nohz_active); -- cgit v1.2.3 From 317f29c14d0cca09952f1022491454b23455ebcb Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Wed, 11 May 2022 13:19:51 -0700 Subject: timers: Provide a better debugobjects hint for delayed works With debugobjects enabled the timer hint for freeing of active timers embedded inside delayed works is always the same, i.e. the hint is delayed_work_timer_fn, even though the function the delayed work is going to run can be wildly different depending on what work was queued. Enabling workqueue debugobjects doesn't help either because the delayed work isn't considered active until it is actually queued to run on a workqueue. If the work is freed while the timer is pending the work isn't considered active so there is no information from workqueue debugobjects. Special case delayed works in the timer debugobjects hint logic so that the delayed work function is returned instead of the delayed_work_timer_fn. This will help to understand which delayed work was pending that got freed. Apply the same treatment for kthread_delayed_work because it follows the same pattern. Suggested-by: Thomas Gleixner Signed-off-by: Stephen Boyd Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220511201951.42408-1-swboyd@chromium.org --- kernel/time/timer.c | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-) (limited to 'kernel/time/timer.c') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index ef082d43c307..a0666d948147 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -638,9 +638,39 @@ static void internal_add_timer(struct timer_base *base, struct timer_list *timer static const struct debug_obj_descr timer_debug_descr; +struct timer_hint { + void (*function)(struct timer_list *t); + long offset; +}; + +#define TIMER_HINT(fn, container, timr, hintfn) \ + { \ + .function = fn, \ + .offset = offsetof(container, hintfn) - \ + offsetof(container, timr) \ + } + +static const struct timer_hint timer_hints[] = { + TIMER_HINT(delayed_work_timer_fn, + struct delayed_work, timer, work.func), + TIMER_HINT(kthread_delayed_work_timer_fn, + struct kthread_delayed_work, timer, work.func), +}; + static void *timer_debug_hint(void *addr) { - return ((struct timer_list *) addr)->function; + struct timer_list *timer = addr; + int i; + + for (i = 0; i < ARRAY_SIZE(timer_hints); i++) { + if (timer_hints[i].function == timer->function) { + void (**fn)(void) = addr + timer_hints[i].offset; + + return *fn; + } + } + + return timer->function; } static bool timer_is_static_object(void *addr) -- cgit v1.2.3 From d4150779e60fb6c49be25572596b2cdfc5d46a09 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 11 May 2022 16:11:29 +0200 Subject: random32: use real rng for non-deterministic randomness MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit random32.c has two random number generators in it: one that is meant to be used deterministically, with some predefined seed, and one that does the same exact thing as random.c, except does it poorly. The first one has some use cases. The second one no longer does and can be replaced with calls to random.c's proper random number generator. The relatively recent siphash-based bad random32.c code was added in response to concerns that the prior random32.c was too deterministic. Out of fears that random.c was (at the time) too slow, this code was anonymously contributed. Then out of that emerged a kind of shadow entropy gathering system, with its own tentacles throughout various net code, added willy nilly. Stop👏making👏bespoke👏random👏number👏generators👏. Fortunately, recent advances in random.c mean that we can stop playing with this sketchiness, and just use get_random_u32(), which is now fast enough. In micro benchmarks using RDPMC, I'm seeing the same median cycle count between the two functions, with the mean being _slightly_ higher due to batches refilling (which we can optimize further need be). However, when doing *real* benchmarks of the net functions that actually use these random numbers, the mean cycles actually *decreased* slightly (with the median still staying the same), likely because the additional prandom code means icache misses and complexity, whereas random.c is generally already being used by something else nearby. The biggest benefit of this is that there are many users of prandom who probably should be using cryptographically secure random numbers. This makes all of those accidental cases become secure by just flipping a switch. Later on, we can do a tree-wide cleanup to remove the static inline wrapper functions that this commit adds. There are also some low-ish hanging fruits for making this even faster in the future: a get_random_u16() function for use in the networking stack will give a 2x performance boost there, using SIMD for ChaCha20 will let us compute 4 or 8 or 16 blocks of output in parallel, instead of just one, giving us large buffers for cheap, and introducing a get_random_*_bh() function that assumes irqs are already disabled will shave off a few cycles for ordinary calls. These are things we can chip away at down the road. Acked-by: Jakub Kicinski Acked-by: Theodore Ts'o Signed-off-by: Jason A. Donenfeld --- kernel/time/timer.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'kernel/time/timer.c') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 9dd2a39cb3b0..c12fe329c9ff 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1780,8 +1780,6 @@ void update_process_times(int user_tick) { struct task_struct *p = current; - PRANDOM_ADD_NOISE(jiffies, user_tick, p, 0); - /* Note: this timer irq context must be accounted for as well. */ account_process_tick(p, user_tick); run_local_timers(); -- cgit v1.2.3