From: Valentin Schneider <valentin.schneider@arm.com>
To: Frederic Weisbecker <frederic@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E . McKenney" <paulmck@kernel.org>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Yejune Deng <yejune.deng@gmail.com>
Subject: Re: [PATCH] sched: Fix PF_NO_SETAFFINITY blind inheritance
Date: Wed, 26 May 2021 11:10:07 +0100 [thread overview]
Message-ID: <87a6ohhklc.mognet@arm.com> (raw)
In-Reply-To: <20210525235849.441842-1-frederic@kernel.org>
Hi Frederic,
Sorry about that one; thanks for having dug into it.
On 26/05/21 01:58, Frederic Weisbecker wrote:
> One way to solve the PF_NO_SETAFFINITY issue is to not inherit this flag
> on copy_process() at all. The cases where it matters are:
>
> * fork_idle(): explicitly set the flag already.
> * fork() syscalls: userspace tasks that shouldn't be concerned by that.
> * create_io_thread(): the callers explicitly attribute the flag to the
> newly created tasks.
> * kernel_thread():
> _ Fix the issues on init/1 and kthreadd
> _ Fix the issues on kthreadd children.
> _ Usermode helper created by an unbound workqueue. This shouldn't
> matter. In the worst case it gives more control to userspace
> on setting affinity to these short living tasks although this can
> be tuned with inherited unbound workqueues affinity already.
>
(I just saw it got shoved into tip already, but in any case:)
That makes sense to me. Regarding the UMH point, I don't believe there are
others like it creeping around; otherwise we might've had to go with e.g.
p->flags &= ~(... | (PF_NO_SETAFFINITY * !!(p->flags & PF_IDLE)))
but per the above that doesn't seem necessary.
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
prev parent reply other threads:[~2021-05-26 10:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-25 23:58 [PATCH] sched: Fix PF_NO_SETAFFINITY blind inheritance Frederic Weisbecker
2021-05-26 7:16 ` [tip: sched/core] sched: Stop PF_NO_SETAFFINITY from being inherited by various init system threads tip-bot2 for Frederic Weisbecker
2021-05-26 10:10 ` Valentin Schneider [this message]
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