From: David Howells <dhowells@redhat.com>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: dhowells@redhat.com, peterz@infradead.org,
linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, mingo@redhat.com,
tglx@linutronix.de, will@kernel.org,
Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH] Revert "locking/mutex: Complain upon mutex API misuse in IRQ contexts"
Date: Tue, 10 Dec 2019 22:32:12 +0000 [thread overview]
Message-ID: <24325.1576017132@warthog.procyon.org.uk> (raw)
In-Reply-To: <20191210220523.28540-1-dave@stgolabs.net>
Davidlohr Bueso <dave@stgolabs.net> wrote:
> This ended up causing some noise in places such as rxrpc running in softirq.
>
> The warning is misleading in this case as the mutex trylock and unlock
> operations are done within the same context; and therefore we need not
> worry about the PI-boosting issues that comes along with no single-owner
> lock guarantees.
>
> While we don't want to support this in mutexes, there is no way out of
> this yet; so lets get rid of the WARNs for now, as it is only fair to
> code that has historically relied on non-preemptible softirq guarantees.
> In addition, changing the lock type is also unviable: exclusive rwsems
> have the same issue (just not the WARN_ON) and counting semaphores
> would introduce a performance hit as mutexes are a lot more optimized.
>
> This reverts commit 5d4ebaa87329ef226e74e52c80ac1c62e4948987.
>
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Tested-by: David Howells <dhowells@redhat.com>
next prev parent reply other threads:[~2019-12-10 22:33 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-10 17:32 [PATCH] rxrpc: Mutexes are unusable from softirq context, so use rwsem instead David Howells
2019-12-10 19:10 ` Peter Zijlstra
2019-12-10 19:30 ` Peter Zijlstra
2019-12-10 22:05 ` [PATCH] Revert "locking/mutex: Complain upon mutex API misuse in IRQ contexts" Davidlohr Bueso
2019-12-10 22:32 ` David Howells [this message]
2019-12-10 23:26 ` Ingo Molnar
2019-12-10 23:35 ` [tip: locking/urgent] " tip-bot2 for Davidlohr Bueso
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