linux-kernel - Re: [PATCH] Fix data race in mark_rt_mutex

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Message-ID: <Y8/+2YBRD4rFySjh@hirez.programming.kicks-ass.net>
Date:   Tue, 24 Jan 2023 16:52:57 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Hernan Ponce de Leon <hernan.poncedeleon@...weicloud.com>,
        paulmck@...nel.org, Arjan van de Ven <arjan@...ux.intel.com>,
        mingo@...hat.com, will@...nel.org, boqun.feng@...il.com,
        akpm@...l.org, tglx@...utronix.de, joel@...lfernandes.org,
        stern@...land.harvard.edu, diogo.behrens@...wei.com,
        jonas.oberhauser@...wei.com, linux-kernel@...r.kernel.org,
        Hernan Ponce de Leon <hernanl.leon@...wei.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH] Fix data race in mark_rt_mutex_waiters

On Tue, Jan 24, 2023 at 10:42:24AM -0500, Waiman Long wrote:

> I would suggest to do it as suggested by PeterZ. Instead of set_bit(),
> however, it is probably better to use atomic_long_or() like
> 
> atomic_long_or_relaxed(RT_MUTEX_HAS_WAITERS, (atomic_long_t *)&lock->owner)

That function doesn't exist, atomic_long_or() is implicitly relaxed for
not returning a value.