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Date:   Sat, 17 Aug 2019 12:43:37 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        "Joel Fernandes, Google" <joel@joelfernandes.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        paulmck <paulmck@linux.ibm.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Will Deacon <will.deacon@arm.com>,
        David Howells <dhowells@redhat.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 1/1] Fix: trace sched switch start/stop racy updates
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On Sat, 17 Aug 2019 11:53:41 -0400 (EDT)
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> kernel/trace/trace.c:tracing_record_taskinfo_sched_switch()
> kernel/trace/trace.c:tracing_record_taskinfo()
> 
> where @flags is used to control a few branches. I don't think any of those
> would end up causing corruption if the flags is re-fetched between two
> branches, but it seems rather fragile.

There shouldn't be any corruption, as each flag test is not dependent
on any of the other tests. But I do agree, a READ_ONCE() would be
appropriate for just making a consistent state among the tests, even
though they are independent.

-- Steve