From: Steven Rostedt <rostedt@goodmis.org>
To: John Stultz <jstultz@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Christian Loehle <christian.loehle@arm.com>,
Qais Yousef <qyousef@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Hongyan Xia <hongyan.xia2@arm.com>,
Ingo Molnar <mingo@kernel.org>, Wei Wang <wvw@google.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>
Subject: Re: Uclamp races due to non-atomic static_branch_likely updates
Date: Tue, 20 Oct 2026 15:29:33 -0400 [thread overview]
Message-ID: <20261020152933.16989549@gandalf.local.home> (raw)
In-Reply-To: <CANDhNCqyXsZ6G77z+9s=rTO6BZifRG9+hVxMTah+tAv6pB6h3w@mail.gmail.com>
On Tue, 20 Oct 2026 11:53:47 -0700
John Stultz <jstultz@google.com> wrote:
> Maybe should the jump_label_update() logic be using something like
> stop_machine? Or should there still be a conditional on key->enabled
> in the unlikely case to make the behavior consistent? Or is there just
> something about the uclamp usage that is off?
There's never been any guarantee that all call sites would update
atomically. The first user of jump labels was tracepoints and I really do
not want stop machine involved with them.
Perhaps we could add an api like static_key_enable_atomic() and
static_key_disable_atomic() that would go through a stop_machine() and
update everything that way for those locations that need an atomic view of
the updated jump labels.
-- Steve
next prev parent reply other threads:[~2026-10-20 19:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-20 18:53 John Stultz
2026-10-20 19:29 ` Steven Rostedt [this message]
2026-10-21 11:38 ` Peter Zijlstra
2026-10-21 13:20 ` Qais Yousef
2026-10-21 13:29 ` Peter Zijlstra
2026-10-21 14:02 ` Qais Yousef
2026-10-21 13:21 ` Steven Rostedt
2026-10-21 13:34 ` Peter Zijlstra
2026-10-21 13:59 ` Steven Rostedt
2026-10-21 17:56 ` John Stultz
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