linux-kernel - Re: [PATCH] workqueue: Fix memory ordering race in queue

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Message-ID: <YvsZ6vObgLaDeSZk@gondor.apana.org.au>
Date:   Tue, 16 Aug 2022 12:15:38 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Tejun Heo <tj@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     marcan@...can.st, will@...nel.org, peterz@...radead.org,
        jirislaby@...nel.org, maz@...nel.org, mark.rutland@....com,
        boqun.feng@...il.com, catalin.marinas@....com, oneukum@...e.com,
        roman.penyaev@...fitbricks.com, asahi@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] workqueue: Fix memory ordering race in queue_work*()

Tejun Heo <tj@...nel.org> wrote:
> 
> Oh, tricky one and yeah you're absolutely right that it makes no sense to
> not guarantee barrier semantics when already pending. I didn't even know
> test_and_set_bit() wasn't a barrier when it failed. Thanks a lot for hunting
> down and fixing this. Applied to wq/for-6.0-fixes.

Please revert this as test_and_set_bit was always supposed to be
a full memory barrier.  This is an arch bug.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt