Date:   Mon, 23 Jan 2023 12:34:37 -0500
From:   Alan Stern <stern@rowland.harvard.edu>
To:     "Paul E. McKenney" <paulmck@kernel.org>
Cc:     Hernan Ponce de Leon <hernan.poncedeleon@huaweicloud.com>,
        Arjan van de Ven <arjan@linux.intel.com>,
        peterz@infradead.org, mingo@redhat.com, will@kernel.org,
        longman@redhat.com, boqun.feng@gmail.com, akpm@osdl.org,
        tglx@linutronix.de, joel@joelfernandes.org,
        diogo.behrens@huawei.com, jonas.oberhauser@huawei.com,
        linux-kernel@vger.kernel.org,
        Hernan Ponce de Leon <hernanl.leon@huawei.com>,
        stable@vger.kernel.org
Subject: Re: [PATCH] Fix data race in mark_rt_mutex_waiters
Message-ID: <Y87FLV0dWSyQz3NZ@rowland.harvard.edu>
References: <20230120135525.25561-1-hernan.poncedeleon@huaweicloud.com>
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 <9a1c7959-4b8c-94df-a3e2-e69be72bfd7d@huaweicloud.com>
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On Mon, Jan 23, 2023 at 08:40:14AM -0800, Paul E. McKenney wrote:
> In the case, the value read is passed into cmpxchg_relaxed(), which
> checks the value against memory.  In this case, as Arjan noted, the only
> compiler-and-silicon difference between data_race() and READ_ONCE()
> is that use of data_race() might allow the compiler to do things like
> tear the load, thus forcing the occasional spurious cmpxchg_relaxed()
> failure.

Is it possible in theory for a torn load to cause a spurious 
cmpxchg_relaxed() success?  Or would that not matter here?

Alan