From: Peter Zijlstra <peterz@infradead.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: Breno Leitao <leitao@debian.org>, Tejun Heo <tj@kernel.org>,
David Vernet <void@manifault.com>,
Changwoo Min <changwoo@igalia.com>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org,
kernel-team@meta.com, jake@hillion.co.uk
Subject: Re: [PATCH] sched/ext: Suppress warning in __this_cpu_write() by disabling preemption
Date: Wed, 16 Jul 2025 15:36:31 +0200 [thread overview]
Message-ID: <20250716133631.GZ905792@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <aHel4LvT_Y5gpYfy@gpd4>
On Wed, Jul 16, 2025 at 03:15:12PM +0200, Andrea Righi wrote:
> The idea is to track the scx callbacks that are invoked with a rq lock held
> and, in those cases, store the locked rq. However, some callbacks may also
> be invoked from an unlocked context, where no rq is locked and in this case
> rq should be NULL.
>
> In the latter case, it's acceptable for preemption to remain enabled, but
> we still want to explicitly set locked_rq = NULL. If during the execution
> of the callback we jump on another CPU, it'd still be in an unlocked state,
> so it's locked_rq is still NULL.
Right; but doing superfluous NULL stores seems pointless. So better to
avoid the store entirely, rather than making it more expensive and no
less pointless, right?
next prev parent reply other threads:[~2025-07-16 13:36 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-16 12:46 Breno Leitao
2025-07-16 12:51 ` Peter Zijlstra
2025-07-16 13:15 ` Andrea Righi
2025-07-16 13:20 ` Breno Leitao
2025-07-16 13:40 ` Peter Zijlstra
2025-07-16 13:36 ` Peter Zijlstra [this message]
2025-07-16 14:26 ` Andrea Righi
2025-07-16 15:49 ` Peter Zijlstra
2025-07-16 16:08 ` Breno Leitao
2025-07-16 16:13 ` Andrea Righi
2025-07-16 12:54 ` Steven Rostedt
2025-07-16 13:06 ` Peter Zijlstra
2025-07-16 13:20 ` Andrea Righi
2025-07-16 13:33 ` Peter Zijlstra
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