Messages in this thread Patch in this message | | | From | Anna-Maria Behnsen <> | Subject | [PATCH v3 17/17] timer: Always queue timers on the local CPU | Date | Tue, 25 Oct 2022 15:58:50 +0200 |
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The timer pull model is in place so we can remove the heuristics which try to guess the best target CPU at enqueue/modification time.
All non pinned timers are queued on the local CPU in the seperate storage and eventually pulled at expiry time to a remote CPU.
When a timer is added via add_timer_on(), TIMER_PINNED flag is required to ensure it expires on the specified CPU. Otherwise it will be enqueued in the global timer base which could be expired by a remote CPU. WARN_ONCE() is added to prevent misuse.
Originally-by: Richard Cochran (linutronix GmbH) <richardcochran@gmail.com> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de> --- kernel/time/timer.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 67f9cc077ff7..f05e547e0c6c 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -947,17 +947,6 @@ static inline struct timer_base *get_timer_base(u32 tflags) return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK); } -static inline struct timer_base * -get_target_base(struct timer_base *base, unsigned tflags) -{ -#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) - if (static_branch_likely(&timers_migration_enabled) && - !(tflags & TIMER_PINNED)) - return get_timer_cpu_base(tflags, get_nohz_timer_target()); -#endif - return get_timer_this_cpu_base(tflags); -} - static inline void forward_timer_base(struct timer_base *base) { unsigned long jnow = READ_ONCE(jiffies); @@ -1093,7 +1082,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option if (!ret && (options & MOD_TIMER_PENDING_ONLY)) goto out_unlock; - new_base = get_target_base(base, timer->flags); + new_base = get_timer_this_cpu_base(timer->flags); if (base != new_base) { /* @@ -1228,6 +1217,10 @@ void add_timer_on(struct timer_list *timer, int cpu) BUG_ON(timer_pending(timer) || !timer->function); + WARN_ONCE(!(timer->flags & TIMER_PINNED), "TIMER_PINNED flag for " + "add_timer_on() is missing: timer=%p function=%ps", + timer, timer->function); + new_base = get_timer_cpu_base(timer->flags, cpu); /* -- 2.30.2
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