From: Herbert Xu <herbert@gondor.apana.org.au>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Will Deacon <will@kernel.org>, Tejun Heo <tj@kernel.org>,
marcan@marcan.st, peterz@infradead.org, jirislaby@kernel.org,
maz@kernel.org, mark.rutland@arm.com, boqun.feng@gmail.com,
catalin.marinas@arm.com, oneukum@suse.com,
roman.penyaev@profitbricks.com, asahi@lists.linux.dev,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] workqueue: Fix memory ordering race in queue_work*()
Date: Tue, 16 Aug 2022 13:48:48 +0800 [thread overview]
Message-ID: <YvsvwCUVtNA5N5+U@gondor.apana.org.au> (raw)
In-Reply-To: <CAHk-=wgSNiT5qJX53RHtWECsUiFq6d6VWYNAvu71ViOEan07yw@mail.gmail.com>
On Mon, Aug 15, 2022 at 10:27:10PM -0700, Linus Torvalds wrote:
>
> The bug seems to go back to commit e986a0d6cb36 ("locking/atomics,
> asm-generic/bitops/atomic.h: Rewrite using atomic_*() APIs"), and the
> fix looks to be as simple as just removing that early READ_ONCE return
> case (test_and_clear has the same bug).
>
> Will?
I think this is the source of all this:
commit 61e02392d3c7ecac1f91c0a90a8043d67e081846
Author: Will Deacon <will@kernel.org>
Date: Tue Feb 13 13:30:19 2018 +0000
locking/atomic/bitops: Document and clarify ordering semantics for failed test_and_{}_bit()
Unfortunately it doesn't work because lots of kernel code rely on
the memory barrier semantics of test_and_set_bit.
If ARM really wants this change, then eitehr create a new API
for it or audit every single existing use in the kernel.
Patching the documentation and then relying on it is magical thinking.
Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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next prev parent reply other threads:[~2022-08-16 5:50 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-15 17:58 [PATCH] workqueue: Fix memory ordering race in queue_work*() Hector Martin
2022-08-15 19:10 ` Tejun Heo
2022-08-16 4:15 ` Herbert Xu
2022-08-16 5:27 ` Linus Torvalds
2022-08-16 5:36 ` Hector Martin
2022-08-16 5:52 ` Linus Torvalds
2022-08-16 6:28 ` Hector Martin
2022-08-16 7:48 ` Herbert Xu
2022-08-16 8:01 ` Hector Martin
2022-08-16 5:48 ` Herbert Xu [this message]
2022-08-16 6:03 ` Linus Torvalds
2022-08-16 13:41 ` Will Deacon
2022-08-16 14:55 ` Boqun Feng
2022-08-16 16:22 ` Hector Martin
2022-08-16 16:43 ` Boqun Feng
2022-08-16 16:58 ` Linus Torvalds
2022-08-16 16:41 ` Linus Torvalds
2022-08-17 5:05 ` Herbert Xu
2022-08-16 17:01 ` Tejun Heo
2022-08-16 16:26 ` Tejun Heo
2022-08-16 17:21 ` Hector Martin
2022-08-16 4:14 ` Herbert Xu
2022-08-16 5:37 ` Hector Martin
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