From: Daniel Bristot de Oliveira <bristot@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] tracing: Quiet smp_processor_id() use in preemptable warning in hwlat
Date: Thu, 5 Aug 2021 08:24:40 +0200 [thread overview]
Message-ID: <072faff2-41d9-11e7-3f85-8ab9dc4b31bc@redhat.com> (raw)
In-Reply-To: <20210804141848.79edadc0@oasis.local.home>
On 8/4/21 8:18 PM, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
>
> The hardware latency detector (hwlat) has a mode that it runs one thread
> across CPUs. The logic to move from the currently running CPU to the next
> one in the list does a smp_processor_id() to find where it currently is.
> Unfortunately, it's done with preemption enabled, and this triggers a
> warning for using smp_processor_id() in a preempt enabled section.
>
> As it is only using smp_processor_id() to get information on where it
> currently is in order to simply move it to the next CPU, it doesn't really
> care if it got moved in the mean time. It will simply balance out later if
> such a case arises.
>
> Switch smp_processor_id() to raw_smp_processor_id() to quiet that warning.
>
> Fixes: 8fa826b7344d ("trace/hwlat: Implement the mode config option")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Thanks!
-- Daniel
> ---
> kernel/trace/trace_hwlat.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
> index a6c0cdaf4b87..14f46aae1981 100644
> --- a/kernel/trace/trace_hwlat.c
> +++ b/kernel/trace/trace_hwlat.c
> @@ -327,7 +327,7 @@ static void move_to_next_cpu(void)
>
> get_online_cpus();
> cpumask_and(current_mask, cpu_online_mask, tr->tracing_cpumask);
> - next_cpu = cpumask_next(smp_processor_id(), current_mask);
> + next_cpu = cpumask_next(raw_smp_processor_id(), current_mask);
> put_online_cpus();
>
> if (next_cpu >= nr_cpu_ids)
>
prev parent reply other threads:[~2021-08-05 6:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-04 18:18 [PATCH] tracing: Quiet smp_processor_id() use in preemptable warning in hwlat Steven Rostedt
2021-08-05 6:24 ` Daniel Bristot de Oliveira [this message]
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