From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, 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>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Valentin Schneider <vschneid@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>,
Joel Fernandes <joel@joelfernandes.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 3/3] sched/nohz: Remove weird error handling from find_new_ilb()
Date: Fri, 6 Oct 2023 13:01:07 +0200 [thread overview]
Message-ID: <ZR/o8+EJGLMi3uPr@gmail.com> (raw)
In-Reply-To: <20231006103858.GB36277@noisy.programming.kicks-ass.net>
* Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, Oct 06, 2023 at 12:25:18PM +0200, Ingo Molnar wrote:
> > find_new_ilb() returns nr_cpu_ids on failure - which is a weird
> > choice in itself: not only is it a global variable, it is
> > a +1 out of bounds CPU index...
>
> FWIW this is what all the cpumask bitops return when they've exhausted
> the mask. Eg. no bits left set etc..
yeah, which then results in type-forcing uglies like:
kernel/events/core.c: if ((unsigned)cpu >= nr_cpu_ids) {
kernel/events/core.c: if ((unsigned)cpu >= nr_cpu_ids) {
kernel/smp.c: if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {
:-/
So I don't think this is a particularly well thought-out interface.
Thanks,
Ingo
next prev parent reply other threads:[~2023-10-06 11:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-06 10:25 [PATCH 0/3] sched/nohz: Misc minor cleanups to the NOHZ idle balancing code Ingo Molnar
2023-10-06 10:25 ` [PATCH 1/3] sched/nohz: Update idle load-balancing (ILB) comments Ingo Molnar
2023-10-09 10:26 ` [tip: sched/core] " tip-bot2 for Ingo Molnar
2023-10-09 15:12 ` [PATCH 1/3] " Valentin Schneider
2023-10-06 10:25 ` [PATCH 2/3] sched/nohz: Use consistent variable names in find_new_ilb() and kick_ilb() Ingo Molnar
2023-10-09 10:26 ` [tip: sched/core] " tip-bot2 for Ingo Molnar
2023-10-09 15:12 ` [PATCH 2/3] " Valentin Schneider
2023-10-06 10:25 ` [PATCH 3/3] sched/nohz: Remove weird error handling from find_new_ilb() Ingo Molnar
2023-10-06 10:38 ` Peter Zijlstra
2023-10-06 11:01 ` Ingo Molnar [this message]
2023-10-09 15:11 ` Valentin Schneider
2023-10-09 10:26 ` [tip: sched/core] sched/nohz: Remove unnecessarily complex error handling pattern " tip-bot2 for Ingo Molnar
2023-10-08 16:56 ` [PATCH 0/3] sched/nohz: Misc minor cleanups to the NOHZ idle balancing code Joel Fernandes
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