From: Haris Okanovic <haris.okanovic@ni.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
julia.cartwright@ni.com, gratian.crisan@ni.com
Subject: Re: [PATCH] Revert "timers: Don't wake ktimersoftd on every tick"
Date: Fri, 26 May 2017 15:25:50 -0500 [thread overview]
Message-ID: <4b4df775-53b8-cdeb-381b-af8cabb364a8@ni.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1705262147510.2137@nanos>
Oh crap. I think I see the problem. I decrement expired_count before
processing the list. Dropping the lock permits another run of
tick_find_expired()->find_expired_timers() in the middle of
__expire_timers() since it uses expired_count==0 as a condition.
This should fix it, but I'll wait for Anna-Maria's test next week before
submitting a patch.
> static void expire_timers(struct timer_base *base)
> {
> struct hlist_head *head;
> + int expCount = base->expired_count;
>
> - while (base->expired_count--) {
> - head = base->expired_lists + base->expired_count;
> + while (expCount--) {
> + head = base->expired_lists + expCount;
> __expire_timers(base, head);
> }
> base->expired_count = 0;
> }
Thanks,
Haris
On 05/26/2017 02:49 PM, Thomas Gleixner wrote:
> On Fri, 26 May 2017, Haris Okanovic wrote:
>
>> Anna-Maria,
>>
>> Look-ahead is implemented by tick_find_expired() and expiry by __run_timers(),
>> both of which hold timer_base::lock (raw spin lock) while running. Those two
>> routines shouldn't be able to run simultaneously on the same timer_base. Are
>> you sure the race isn't in another code path?
>
> It happens when softirq runs and drops the spinlock to call the timer
> function. And from there stuff goes down the drain.
>
> Anna-Maria will send you the test case on monday.
>
> Thanks,
>
> tglx
>
>
>
next prev parent reply other threads:[~2017-05-27 1:14 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-13 21:44 [RFC v2] timers: Don't wake ktimersoftd on every tick Haris Okanovic
2016-12-23 17:28 ` Sebastian Andrzej Siewior
2016-12-28 18:06 ` Haris Okanovic
2017-02-03 16:51 ` Sebastian Andrzej Siewior
2017-02-03 18:21 ` [PATCH] " Haris Okanovic
2017-02-10 17:02 ` Sebastian Andrzej Siewior
2017-05-26 17:16 ` [PATCH] Revert "timers: Don't wake ktimersoftd on every tick" Anna-Maria Gleixner
2017-05-26 19:27 ` Haris Okanovic
2017-05-26 19:49 ` Thomas Gleixner
2017-05-26 20:25 ` Haris Okanovic [this message]
2017-05-26 20:50 ` Thomas Gleixner
2017-06-02 14:37 ` Haris Okanovic
2017-06-04 14:17 ` Thomas Gleixner
2017-07-17 21:58 ` Haris Okanovic
2017-07-17 22:04 ` [PATCH v2] timers: Don't wake ktimersoftd on every tick Haris Okanovic
2017-07-18 21:33 ` Thomas Gleixner
2017-08-03 21:04 ` Haris Okanovic
2017-08-03 21:06 ` [PATCH v3 1/2] " Haris Okanovic
2017-08-03 21:06 ` [PATCH v3 2/2] timers: Don't search for expired timers while TIMER_SOFTIRQ is scheduled Haris Okanovic
2018-01-05 19:37 ` Haris Okanovic
2018-03-01 15:49 ` Haris Okanovic
2018-03-01 15:54 ` Thomas Gleixner
2018-03-01 16:35 ` Haris Okanovic
2018-03-01 16:47 ` Sebastian Andrzej Siewior
2018-03-01 18:37 ` Haris Okanovic
2018-03-01 19:06 ` Sebastian Andrzej Siewior
2018-03-02 14:52 ` Sebastian Andrzej Siewior
2018-03-02 16:29 ` Haris Okanovic
2018-03-02 16:39 ` Sebastian Andrzej Siewior
2018-03-02 17:19 ` Haris Okanovic
2018-03-06 23:39 ` [PATCH v4 1/2] timers: Don't wake ktimersoftd on every tick Haris Okanovic
2018-03-06 23:39 ` [PATCH v4 2/2] timers: Don't search for expired timers while TIMER_SOFTIRQ is scheduled Haris Okanovic
[not found] ` <1523332961.4827.1.camel@gmx.de>
2018-04-12 15:00 ` [PATCH v4 1/2] timers: Don't wake ktimersoftd on every tick Haris Okanovic
2018-06-19 12:43 ` Daniel Bristot de Oliveira
2018-06-20 14:24 ` Haris Okanovic
2018-06-28 16:36 ` Haris Okanovic
2018-06-28 16:40 ` [PATCH v5 " Haris Okanovic
2018-06-28 16:40 ` [PATCH v5 2/2] timers: Don't search for expired timers while TIMER_SOFTIRQ is scheduled Haris Okanovic
2018-07-13 12:01 ` [PATCH v5 1/2] timers: Don't wake ktimersoftd on every tick Anna-Maria Gleixner
2018-07-13 14:37 ` Haris Okanovic
2017-05-27 7:47 ` [PATCH] Revert "timers: Don't wake ktimersoftd on every tick" Sebastian Andrzej Siewior
2017-02-03 18:27 ` [RFC v2] timers: Don't wake ktimersoftd on every tick Haris Okanovic
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