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From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, x86@kernel.org,
	cai@lca.pw, mgorman@techsingularity.net
Subject: Re: [RFC][PATCH 1/7] sched: Fix smp_call_function_single_async() usage for ILB
Date: Wed, 27 May 2020 01:56:34 +0200	[thread overview]
Message-ID: <20200526235632.GA8942@lenoir> (raw)
In-Reply-To: <20200526161907.778543557@infradead.org>

On Tue, May 26, 2020 at 06:10:58PM +0200, Peter Zijlstra wrote:
> The recent commit: 90b5363acd47 ("sched: Clean up scheduler_ipi()")
> got smp_call_function_single_async() subtly wrong. Even though it will
> return -EBUSY when trying to re-use a csd, that condition is not
> atomic and still requires external serialization.
> 
> The change in kick_ilb() got this wrong.
> 
> While on first reading kick_ilb() has an atomic test-and-set that
> appears to serialize the use, the matching 'release' is not in the
> right place to actually guarantee this serialization.
> 
> Rework the nohz_idle_balance() trigger so that the release is in the
> IPI callback and thus guarantees the required serialization for the
> CSD.
> 
> Fixes: 90b5363acd47 ("sched: Clean up scheduler_ipi()")
> Reported-by: Qian Cai <cai@lca.pw>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Looks very good! Thanks!

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

  reply	other threads:[~2020-05-26 23:56 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-26 16:10 [RFC][PATCH 0/7] Fix the scheduler-IPI mess Peter Zijlstra
2020-05-26 16:10 ` [RFC][PATCH 1/7] sched: Fix smp_call_function_single_async() usage for ILB Peter Zijlstra
2020-05-26 23:56   ` Frederic Weisbecker [this message]
2020-05-27 10:23   ` Vincent Guittot
2020-05-27 11:28     ` Frederic Weisbecker
2020-05-27 12:07       ` Vincent Guittot
2020-05-29 15:26   ` Valentin Schneider
2020-06-01  9:52   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-06-01 11:40     ` Frederic Weisbecker
2020-05-26 16:10 ` [RFC][PATCH 2/7] smp: Optimize flush_smp_call_function_queue() Peter Zijlstra
2020-05-28 12:28   ` Frederic Weisbecker
2020-06-01  9:52   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-05-26 16:11 ` [RFC][PATCH 3/7] smp: Move irq_work_run() out of flush_smp_call_function_queue() Peter Zijlstra
2020-05-29 13:04   ` Frederic Weisbecker
2020-06-01  9:52   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-05-26 16:11 ` [RFC][PATCH 4/7] smp: Optimize send_call_function_single_ipi() Peter Zijlstra
2020-05-27  7:01   ` kbuild test robot
2020-05-27  9:56   ` Peter Zijlstra
2020-05-27 10:15     ` Peter Zijlstra
2020-05-27 15:56       ` Paul E. McKenney
2020-05-27 16:35         ` Peter Zijlstra
2020-05-27 17:12           ` Peter Zijlstra
2020-05-27 19:39             ` Paul E. McKenney
2020-05-28  1:35               ` Joel Fernandes
2020-05-28  8:59             ` [tip: core/rcu] rcu: Allow for smp_call_function() running callbacks from idle tip-bot2 for Peter Zijlstra
2021-01-21 16:56             ` [RFC][PATCH 4/7] smp: Optimize send_call_function_single_ipi() Peter Zijlstra
2021-01-22  0:20               ` Paul E. McKenney
2021-01-22  8:31                 ` Peter Zijlstra
2021-01-22 15:35                   ` Paul E. McKenney
2020-05-29  1:19   ` kbuild test robot
2020-05-29 11:18     ` Peter Zijlstra
2020-05-30  1:07       ` Philip Li
2020-05-29 13:01   ` Frederic Weisbecker
2020-06-01  9:52   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-05-26 16:11 ` [RFC][PATCH 5/7] irq_work, smp: Allow irq_work on call_single_queue Peter Zijlstra
2020-05-28 23:40   ` Frederic Weisbecker
2020-05-29 13:36     ` Peter Zijlstra
2020-06-05  9:37       ` Peter Zijlstra
2020-06-05 15:02         ` Frederic Weisbecker
2020-06-05 16:17           ` Peter Zijlstra
2020-06-05 15:24         ` Kees Cook
2020-06-10 13:24         ` Frederic Weisbecker
2020-06-01  9:52   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-05-26 16:11 ` [RFC][PATCH 6/7] sched: Add rq::ttwu_pending Peter Zijlstra
2020-06-01  9:52   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-05-26 16:11 ` [RFC][PATCH 7/7] sched: Replace rq::wake_list Peter Zijlstra
2020-05-29 15:10   ` Valdis Klētnieks
2020-06-01  9:52   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-06-02 15:16     ` Frederic Weisbecker
2020-06-04 14:18   ` [RFC][PATCH 7/7] " Guenter Roeck
2020-06-05  0:24     ` Eric Biggers
2020-06-05  7:41       ` Peter Zijlstra
2020-06-05 16:15         ` Eric Biggers
2020-06-06 23:13           ` Guenter Roeck
2020-06-09 20:21             ` Eric Biggers
2020-06-09 21:25               ` Guenter Roeck
2020-06-09 21:38                 ` Eric Biggers
2020-06-09 22:06                   ` Peter Zijlstra
2020-06-09 23:03                     ` Guenter Roeck
2020-06-10  9:09                       ` Peter Zijlstra
2020-06-18 17:57                 ` Steven Rostedt
2020-06-18 19:06                   ` Guenter Roeck
2020-06-09 22:07               ` Peter Zijlstra
2020-06-05  8:10     ` Peter Zijlstra
2020-06-05 13:33       ` Guenter Roeck
2020-06-05 14:09         ` Peter Zijlstra

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