From 3bb475a3446facd0425d3f2fe7e85bf03c5c6c05 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 26 May 2015 22:50:24 +0000 Subject: [PATCH] timers: Sanitize catchup_timer_jiffies() usage catchup_timer_jiffies() has been applied blindly to several functions without looking for possible better ways to do it. 1) internal_add_timer() Move the update to base->all_timers before we actually insert the timer into the wheel. 2) detach_if_pending() Again the update to base->all_timers allows us to explicitely do the timer_jiffies update in place, if this was the last timer which got removed. 3) __run_timers() We only check on entry, which is silly, because base->timer_jiffies can be behind - especially on NOHZ kernels - and if there is a single deferrable timer somewhere between base->timer_jiffies and jiffies we expire it and then loop until base->timer_jiffies == jiffies. Move it into the loop. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Paul McKenney Cc: Frederic Weisbecker Cc: Eric Dumazet Cc: Viresh Kumar Cc: John Stultz Cc: Joonwoo Park Cc: Wenbo Wang Link: http://lkml.kernel.org/r/20150526224511.662994644@linutronix.de Signed-off-by: Thomas Gleixner --- kernel/time/timer.c | 40 ++++++++++++++++------------------------ 1 file changed, 16 insertions(+), 24 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 7775d454a204..d5e017970ac7 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -351,20 +351,6 @@ void set_timer_slack(struct timer_list *timer, int slack_hz) } EXPORT_SYMBOL_GPL(set_timer_slack); -/* - * If the list is empty, catch up ->timer_jiffies to the current time. - * The caller must hold the tvec_base lock. Returns true if the list - * was empty and therefore ->timer_jiffies was updated. - */ -static bool catchup_timer_jiffies(struct tvec_base *base) -{ - if (!base->all_timers) { - base->timer_jiffies = jiffies; - return true; - } - return false; -} - static void __internal_add_timer(struct tvec_base *base, struct timer_list *timer) { @@ -411,7 +397,10 @@ __internal_add_timer(struct tvec_base *base, struct timer_list *timer) static void internal_add_timer(struct tvec_base *base, struct timer_list *timer) { - (void)catchup_timer_jiffies(base); + /* Advance base->jiffies, if the base is empty */ + if (!base->all_timers++) + base->timer_jiffies = jiffies; + __internal_add_timer(base, timer); /* * Update base->active_timers and base->next_timer @@ -421,7 +410,6 @@ static void internal_add_timer(struct tvec_base *base, struct timer_list *timer) time_before(timer->expires, base->next_timer)) base->next_timer = timer->expires; } - base->all_timers++; /* * Check whether the other CPU is in dynticks mode and needs @@ -718,7 +706,6 @@ detach_expired_timer(struct timer_list *timer, struct tvec_base *base) if (!tbase_get_deferrable(timer->base)) base->active_timers--; base->all_timers--; - (void)catchup_timer_jiffies(base); } static int detach_if_pending(struct timer_list *timer, struct tvec_base *base, @@ -733,8 +720,9 @@ static int detach_if_pending(struct timer_list *timer, struct tvec_base *base, if (timer->expires == base->next_timer) base->next_timer = base->timer_jiffies; } - base->all_timers--; - (void)catchup_timer_jiffies(base); + /* If this was the last timer, advance base->jiffies */ + if (!--base->all_timers) + base->timer_jiffies = jiffies; return 1; } @@ -1184,14 +1172,18 @@ static inline void __run_timers(struct tvec_base *base) struct timer_list *timer; spin_lock_irq(&base->lock); - if (catchup_timer_jiffies(base)) { - spin_unlock_irq(&base->lock); - return; - } + while (time_after_eq(jiffies, base->timer_jiffies)) { struct list_head work_list; struct list_head *head = &work_list; - int index = base->timer_jiffies & TVR_MASK; + int index; + + if (!base->all_timers) { + base->timer_jiffies = jiffies; + break; + } + + index = base->timer_jiffies & TVR_MASK; /* * Cascade timers: -- GitLab