From: Steven Rostedt <rostedt@goodmis.org>
To: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Phil Auld <pauld@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Kate Carcia <kcarcia@redhat.com>,
Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Clark Willaims <williams@redhat.com>,
John Kacur <jkacur@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V5 12/14] trace: Protect tr->tracing_cpumask with get/put_online_cpus
Date: Thu, 24 Jun 2021 17:39:02 -0400 [thread overview]
Message-ID: <20210624173902.57f4f34f@oasis.local.home> (raw)
In-Reply-To: <38d2ef13b33c42fcf424a6213a27c8b5246548e0.1624372313.git.bristot@redhat.com>
On Tue, 22 Jun 2021 16:42:30 +0200
Daniel Bristot de Oliveira <bristot@redhat.com> wrote:
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 52fc9438b7b4..c14f33db147e 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5053,7 +5053,13 @@ int tracing_set_cpumask(struct trace_array *tr,
> arch_spin_unlock(&tr->max_lock);
> local_irq_enable();
>
> + /*
> + * tracing_cpumask is read by tracers that support CPU
> + * hotplug.
> + */
> + get_online_cpus();
> cpumask_copy(tr->tracing_cpumask, tracing_cpumask_new);
> + put_online_cpus();
>
> return 0;
Hmm, the tracing_cpumask is only touched in he work function, with the
necessary locks. How is get_online_cpus() protecting it here?
That is, tracing_cpumask isn't touched in the path of bringing up or
taking down a CPU, and shouldn't be an issue here.
Should I just drop this patch?
-- Steve
next prev parent reply other threads:[~2021-06-24 21:39 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-22 14:42 [PATCH V5 00/14] hwlat improvements and osnoise/timerlat tracers Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 01/14] trace/hwlat: Fix Clark's email Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 02/14] trace/hwlat: Implement the mode config option Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 03/14] trace/hwlat: Switch disable_migrate to mode none Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 04/14] trace/hwlat: Implement the per-cpu mode Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 05/14] trace: Add a generic function to read/write u64 values from tracefs Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 06/14] trace/hwlat: Use trace_min_max_param for width and window params Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 07/14] trace/hwlat: Remove printk from sampling loop Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 08/14] trace: Add __print_ns_to_secs() and __print_ns_without_secs() helpers Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 09/14] trace: Add osnoise tracer Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 10/14] trace: Add timerlat tracer Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 11/14] trace/hwlat: Protect kdata->kthread with get/put_online_cpus Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 12/14] trace: Protect tr->tracing_cpumask " Daniel Bristot de Oliveira
2021-06-24 21:39 ` Steven Rostedt [this message]
2021-06-25 4:34 ` Daniel Bristot de Oliveira
2021-06-25 9:27 ` Peter Zijlstra
2021-06-25 9:31 ` Sebastian Andrzej Siewior
2021-06-22 14:42 ` [PATCH V5 13/14] trace/hwlat: Support hotplug operations Daniel Bristot de Oliveira
2021-06-22 14:42 ` [PATCH V5 14/14] trace/osnoise: " Daniel Bristot de Oliveira
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