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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 <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Joonwoo Park <joonwoop@codeaurora.org>
Cc: Wenbo Wang <wenbo.wang@memblaze.com>
Link: http://lkml.kernel.org/r/20150526224511.662994644@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
hifive-unleashed-5.1
Thomas Gleixner 2015-05-26 22:50:24 +00:00
parent 887d9dc989
commit 3bb475a344
1 changed files with 16 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
kernel/time/timer.c
View File

@ -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: