From: tip-bot for Thomas Gleixner <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, john.stultz@linaro.org,
joonwoop@codeaurora.org, fweisbec@gmail.com, edumazet@google.com,
wenbo.wang@memblaze.com, hpa@zytor.com, peterz@infradead.org,
tglx@linutronix.de, viresh.kumar@linaro.org, mingo@kernel.org,
paulmck@linux.vnet.ibm.com
Subject: [tip:timers/core] timers: Sanitize catchup_timer_jiffies() usage
Date: Fri, 19 Jun 2015 06:22:24 -0700 [thread overview]
Message-ID: <tip-3bb475a3446facd0425d3f2fe7e85bf03c5c6c05@git.kernel.org> (raw)
In-Reply-To: <20150526224511.662994644@linutronix.de>
Commit-ID: 3bb475a3446facd0425d3f2fe7e85bf03c5c6c05
Gitweb: http://git.kernel.org/tip/3bb475a3446facd0425d3f2fe7e85bf03c5c6c05
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Tue, 26 May 2015 22:50:24 +0000
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 19 Jun 2015 15:18:27 +0200
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>
---
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 7775d45..d5e0179 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:
--
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next prev parent reply other threads:[~2015-06-19 13:24 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-26 22:50 [patch 0/7] timers: Footprint diet and NOHZ overhead mitigation Thomas Gleixner
2015-05-26 22:50 ` [patch 1/7] timers: Sanitize catchup_timer_jiffies() usage Thomas Gleixner
2015-05-27 5:39 ` Viresh Kumar
2015-06-19 13:22 ` tip-bot for Thomas Gleixner [this message]
2015-05-26 22:50 ` [patch 2/7] timer: Remove FIFO guarantee Thomas Gleixner
2015-05-27 9:11 ` Viresh Kumar
2015-06-19 13:22 ` [tip:timers/core] timer: Remove FIFO "guarantee" tip-bot for Thomas Gleixner
2015-05-26 22:50 ` [patch 3/7] timer: Use hlist for the timer wheel hash buckets Thomas Gleixner
2015-05-27 9:13 ` Viresh Kumar
2015-06-19 13:23 ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-05-26 22:50 ` [patch 4/7] timer: Replace timer base by a cpu index Thomas Gleixner
2015-05-27 9:22 ` Viresh Kumar
2015-05-27 12:09 ` Peter Zijlstra
2015-06-02 13:58 ` Thomas Gleixner
2015-06-19 13:23 ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-06-27 9:55 ` [PATCH] timer: Fix unsafe cpu variable access in migrate_timers Jan Kiszka
2015-06-27 11:00 ` Borislav Petkov
2015-06-27 11:19 ` Jan Kiszka
2015-06-27 11:25 ` Borislav Petkov
2015-05-26 22:50 ` [patch 5/7] timer: stats: Simplify the flags handling Thomas Gleixner
2015-06-19 13:23 ` [tip:timers/core] timer: Stats: " tip-bot for Thomas Gleixner
2015-05-26 22:50 ` [patch 6/7] timer: Reduce timer migration overhead if disabled Thomas Gleixner
2015-06-19 13:23 ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-05-26 22:50 ` [patch 7/7] timer: Minimize nohz off overhead Thomas Gleixner
2015-06-19 13:24 ` [tip:timers/core] " tip-bot for Thomas Gleixner
2015-05-27 14:53 ` [patch 0/7] timers: Footprint diet and NOHZ overhead mitigation Eric Dumazet
2015-06-02 13:58 ` Thomas Gleixner
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