From: Hector Martin <marcan@marcan.st>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Will Deacon <will@kernel.org>, Tejun Heo <tj@kernel.org>,
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 17:01:39 +0900 [thread overview]
Message-ID: <0c0ba856-a4ba-7133-e751-3a81c82311a9@marcan.st> (raw)
In-Reply-To: <YvtLsNZEUUytdx+i@gondor.apana.org.au>
On 2022/08/16 16:48, Herbert Xu wrote:
> On Tue, Aug 16, 2022 at 03:28:50PM +0900, Hector Martin wrote:
>>
>> This is the same reason I argued queue_work() itself needs to have a
>> similar guarantee, even when it doesn't queue work (and I updated the
>> doc to match). If test_and_set_bit() is used in this kind of context
>> often in the kernel, clearly the current implementation/doc clashes with
>> that.
>
> Kernel code all over the place rely on the fact that test_and_set_bit
> provides a memory barrier. So this bug that you've discovered is
> not at all isolated to the workqeueue system. It'll break the kernel
> in lots of places in exactly the same way.
Now I'm surprised this isn't failing all over the place, given that...
these things are annoyingly subtle.
Still would want Will & Peter to chime in, of course.
>> As I said, I don't have any particular beef in this fight, but this is
>> horribly broken on M1/2 right now, so I'll send a patch to change the
>> bitops instead and you all can fight it out over which way is correct :)
>
> Please do.
Already did, but I just realized I forgot to Cc you. Sorry about that,
hope you can pick it up through the MLs:
https://lore.kernel.org/asahi/20220816070311.89186-1-marcan@marcan.st/T/#u
- Hector
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next prev parent reply other threads:[~2022-08-16 8:03 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 [this message]
2022-08-16 5:48 ` Herbert Xu
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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