From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Eric Dumazet <edumazet@google.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
John Stultz <john.stultz@linaro.org>,
Joonwoo Park <joonwoop@codeaurora.org>,
Wenbo Wang <wenbo.wang@memblaze.com>
Subject: [patch 1/7] timers: Sanitize catchup_timer_jiffies() usage
Date: Tue, 26 May 2015 22:50:24 -0000 [thread overview]
Message-ID: <20150526224511.662994644@linutronix.de> (raw)
In-Reply-To: 20150526210723.245729529@linutronix.de
[-- Attachment #1: timers-sanitize-catchup-jiffies.patch --]
[-- Type: text/plain, Size: 3247 bytes --]
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>
---
kernel/time/timer.c | 26 +++++++++++++++-----------
1 file changed, 15 insertions(+), 11 deletions(-)
Index: tip/kernel/time/timer.c
===================================================================
--- tip.orig/kernel/time/timer.c
+++ tip/kernel/time/timer.c
@@ -356,7 +356,7 @@ EXPORT_SYMBOL_GPL(set_timer_slack);
* 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)
+static inline bool catchup_timer_jiffies(struct tvec_base *base)
{
if (!base->all_timers) {
base->timer_jiffies = jiffies;
@@ -411,7 +411,10 @@ __internal_add_timer(struct tvec_base *b
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 +424,6 @@ static void internal_add_timer(struct tv
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
@@ -719,7 +721,6 @@ detach_expired_timer(struct timer_list *
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,
@@ -734,8 +735,9 @@ static int detach_if_pending(struct time
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;
}
@@ -1185,14 +1187,16 @@ static inline void __run_timers(struct t
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 (catchup_timer_jiffies(base))
+ break;
+
+ index = base->timer_jiffies & TVR_MASK;
/*
* Cascade timers:
next prev parent reply other threads:[~2015-05-26 22:50 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 ` Thomas Gleixner [this message]
2015-05-27 5:39 ` [patch 1/7] timers: Sanitize catchup_timer_jiffies() usage Viresh Kumar
2015-06-19 13:22 ` [tip:timers/core] " tip-bot for Thomas Gleixner
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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