From: Bart Van Assche <bvanassche@acm.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: "Ionut Nechita (Wind River)" <ionut.nechita@windriver.com>,
axboe@kernel.dk, linux-block@vger.kernel.org,
clrkwllms@kernel.org, rostedt@goodmis.org, ming.lei@redhat.com,
muchun.song@linux.dev, mkhalfella@purestorage.com,
chris.friesen@windriver.com, linux-kernel@vger.kernel.org,
linux-rt-devel@lists.linux.dev, linux-rt-users@vger.kernel.org,
stable@vger.kernel.org, ionut_n2001@yahoo.com,
sunlightlinux@gmail.com
Subject: Re: [PATCH v6 1/1] block/blk-mq: use atomic_t for quiesce_depth to avoid lock contention on RT
Date: Wed, 6 May 2026 11:43:32 +0200 [thread overview]
Message-ID: <713ba2ae-e322-4e56-b0b8-89766f7f65c1@acm.org> (raw)
In-Reply-To: <20260506074758.8zEg1ZBh@linutronix.de>
On 5/6/26 9:47 AM, Sebastian Andrzej Siewior wrote:
> On 2026-05-06 09:14:33 [+0200], Bart Van Assche wrote:
>> If the atomic_inc() in blk_mq_quiesce_queue_nowait() is protected by
>> hctx->queue->queue_lock then the above code doesn't have to be modified.
>
> But wouldn't the atomic_inc + barrier avoid the need to have the lock?
> Isn't this a normal pattern? If the lock is kept, we could use
> non-atomic ops here then. But this avoids having the lock.
I strongly prefer a spinlock + non-atomic variables rather than using an
atomic variable and barriers because algorithms that use a spinlock are
easier to verify.
Thanks,
Bart.
prev parent reply other threads:[~2026-05-06 9:43 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-06 6:56 [PATCH v6 0/1] block/blk-mq: use atomic_t for quiesce_depth to avoid lock contention on RT Ionut Nechita (Wind River)
2026-05-06 6:56 ` [PATCH v6 1/1] " Ionut Nechita (Wind River)
2026-05-06 7:14 ` Bart Van Assche
2026-05-06 7:47 ` Sebastian Andrzej Siewior
2026-05-06 9:43 ` Bart Van Assche [this message]
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