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From: Ming Lei <ming.lei@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v2] blk-mq: Don't disable preemption around __blk_mq_run_hw_queue().
Date: Wed, 22 Jun 2022 16:35:46 +0800	[thread overview]
Message-ID: <YrLUYvEaKeW6Mmfd@T590> (raw)
In-Reply-To: <YrLSEiNvagKJaDs5@linutronix.de>

On Wed, Jun 22, 2022 at 10:25:54AM +0200, Sebastian Andrzej Siewior wrote:
> __blk_mq_delay_run_hw_queue() disables preemption to get a stable
> current CPU number and then invokes __blk_mq_run_hw_queue() if the CPU
> number is part the mask.
> 
> __blk_mq_run_hw_queue() acquires a spin_lock_t which is a sleeping lock
> on PREEMPT_RT and can't be acquired with disabled preemption.
> 
> It is not required for correctness to invoke __blk_mq_run_hw_queue() on
> a CPU matching hctx->cpumask. Both (async and direct requests) can run
> on a CPU not matching hctx->cpumask.
> 
> The CPU mask without disabling preemption and invoking
> __blk_mq_run_hw_queue().
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Looks fine:

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming


  reply	other threads:[~2022-06-22  8:36 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-21  7:39 [PATCH REPOST] blk-mq: Don't disable preemption around __blk_mq_run_hw_queue() Sebastian Andrzej Siewior
2022-06-21  7:56 ` Ming Lei
2022-06-22  8:25   ` [PATCH v2] " Sebastian Andrzej Siewior
2022-06-22  8:35     ` Ming Lei [this message]
2022-06-22 17:46     ` Jens Axboe

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