linux-kernel - [PATCH V5 12/14] trace: Protect tr->tracing_cpumask with get/put_online

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Message-Id: <38d2ef13b33c42fcf424a6213a27c8b5246548e0.1624372313.git.bristot@redhat.com>
Date:   Tue, 22 Jun 2021 16:42:30 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Phil Auld <pauld@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Kate Carcia <kcarcia@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Clark Willaims <williams@...hat.com>,
        John Kacur <jkacur@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH V5 12/14] trace: Protect tr->tracing_cpumask with get/put_online_cpus

In preparation to the hotplug support on tracers with workload,
protect tr->tracing_cpumask with get/put_online_cpus() to avoid
concurrency with hotplug operations.

Cc: Jonathan Corbet <corbet@....net>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Alexandre Chartre <alexandre.chartre@...cle.com>
Cc: Clark Willaims <williams@...hat.com>
Cc: John Kacur <jkacur@...hat.com>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
Cc: linux-doc@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
---
 kernel/trace/trace.c | 6 ++++++
 1 file changed, 6 insertions(+)

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;
 }
-- 
2.31.1