From: Peter Zijlstra <peterz@infradead.org>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: akpm@linux-foundation.org, tglx@linutronix.de, mingo@kernel.org,
mgorman@techsingularity.net, bp@suse.de,
linux-kernel@vger.kernel.org, Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH] kernel/sys: do not use tasklist_lock to set/get scheduling priorities
Date: Sat, 2 May 2020 11:31:05 +0200 [thread overview]
Message-ID: <20200502093105.GJ3762@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200502030539.32581-1-dave@stgolabs.net>
On Fri, May 01, 2020 at 08:05:39PM -0700, Davidlohr Bueso wrote:
> For both setpriority(2) and getpriority(2) there's really no need
> to be taking the tasklist_lock at all - for which both share it
> for the entirety of the syscall. The tasklist_lock does not protect
> reading/writing the p->static_prio and task lookups are already rcu
> safe, providing a stable pointer.
RCU-safe, as in, it will not crash.. However, without tasklist_lock the
thread iterations (for PRIO_PGRP/PRIO_USER) now race against fork().
That is a user observable change in behaviour.
Do we care about it? No idea, and your Changelog also doesn't provide
clue.
next prev parent reply other threads:[~2020-05-02 9:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-02 3:05 Davidlohr Bueso
2020-05-02 9:31 ` Peter Zijlstra [this message]
2020-05-03 20:43 ` Davidlohr Bueso
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