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From: David Miller <davem@davemloft.net>
To: bigeasy@linutronix.de
Cc: sergei.shtylyov@cogentembedded.com, netdev@vger.kernel.org,
	jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us,
	edumazet@google.com, tglx@linutronix.de, mkl@pengutronix.de,
	peterz@infradead.org
Subject: Re: [PATCH net-next v2] net: sched: Avoid using yield() in a busy waiting loop
Date: Thu, 17 Oct 2019 15:33:40 -0400 (EDT)	[thread overview]
Message-ID: <20191017.153340.1998610553660604312.davem@davemloft.net> (raw)
In-Reply-To: <20191016082833.u4jxbiqg3oo6lyue@linutronix.de>

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 16 Oct 2019 10:28:33 +0200

> From: Marc Kleine-Budde <mkl@pengutronix.de>
> 
> With threaded interrupts enabled, the interrupt thread runs as SCHED_RR
> with priority 50. If a user application with a higher priority preempts
> the interrupt thread and tries to shutdown the network interface then it
> will loop forever. The kernel will spin in the loop waiting for the
> device to become idle and the scheduler will never consider the
> interrupt thread because its priority is lower.
> 
> Avoid the problem by sleeping for a jiffy giving other tasks,
> including the interrupt thread, a chance to run and make progress.
> 
> In the original thread it has been suggested to use wait_event() and
> properly waiting for the state to occur. DaveM explained that this would
> require to add expensive checks in the fast paths of packet processing.
> 
> Link: https://lkml.kernel.org/r/1393976987-23555-1-git-send-email-mkl@pengutronix.de
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> [bigeasy: Rewrite commit message, add comment, use
>           schedule_timeout_uninterruptible()]
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> v1…v2: Typo fixes, noticed by Sergei Shtylyov.

Applied, thank you.

      parent reply	other threads:[~2019-10-17 19:33 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-11 17:15 [PATCH net-next] net: sched: Avoid using yield() in a busy waiting loop Sebastian Andrzej Siewior
2019-10-12 19:14 ` Sergei Shtylyov
2019-10-16  8:28   ` [PATCH net-next v2] " Sebastian Andrzej Siewior
2019-10-16 17:28     ` Cong Wang
2019-10-16 18:48       ` Sebastian Andrzej Siewior
2019-10-16 21:33         ` Cong Wang
2019-10-17 19:33     ` David Miller [this message]

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