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From: Daniel Wagner <dwagner@suse.de>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 3/3 v2] blk-mq: Use llist_head for blk_cpu_done
Date: Wed, 27 Jan 2021 12:23:31 +0100	[thread overview]
Message-ID: <20210127112331.bew6os5jfyvjzhwj@beryllium.lan> (raw)
In-Reply-To: <20210125095412.qxknd2vbsmgtrhqb@linutronix.de>

On Mon, Jan 25, 2021 at 10:54:12AM +0100, Sebastian Andrzej Siewior wrote:
> With llist_head it is possible to avoid the locking (the irq-off region)
> when items are added. This makes it possible to add items on a remote
> CPU without additional locking.
> llist_add() returns true if the list was previously empty. This can be
> used to invoke the SMP function call / raise sofirq only if the first
> item was added (otherwise it is already pending).
> This simplifies the code a little and reduces the IRQ-off regions.
> 
> blk_mq_raise_softirq() needs a preempt-disable section to ensure the
> request is enqueued on the same CPU as the softirq is raised.
> Some callers (USB-storage) invoke this path in preemptible context.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

I did a quick test run with the whole series. Looks good.

Reviewed-by: Daniel Wagner <dwagner@suse.de>

  parent reply	other threads:[~2021-01-27 11:26 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-23 20:10 [PATCH v3 0/3] blk-mq: Don't complete in IRQ, use llist_head Sebastian Andrzej Siewior
2021-01-23 20:10 ` [PATCH 1/3] smp: Process pending softirqs in flush_smp_call_function_from_idle() Sebastian Andrzej Siewior
2021-02-01 19:35   ` Sebastian Andrzej Siewior
2021-02-09 10:02   ` Peter Zijlstra
2021-02-09 11:35     ` Sebastian Andrzej Siewior
2021-02-10 13:53   ` [tip: sched/core] " tip-bot2 for Sebastian Andrzej Siewior
2021-02-17 13:17   ` tip-bot2 for Sebastian Andrzej Siewior
2021-01-23 20:10 ` [PATCH 2/3] blk-mq: Always complete remote completions requests in softirq Sebastian Andrzej Siewior
2021-01-25  7:10   ` Hannes Reinecke
2021-01-25  8:25     ` Christoph Hellwig
2021-01-25  8:30       ` Sebastian Andrzej Siewior
2021-01-25  8:32         ` Christoph Hellwig
2021-01-25  9:29           ` Sebastian Andrzej Siewior
2021-01-25  8:22   ` Christoph Hellwig
2021-01-25  8:49     ` Christoph Hellwig
2021-01-27 11:22   ` Daniel Wagner
2021-01-23 20:10 ` [PATCH 3/3] blk-mq: Use llist_head for blk_cpu_done Sebastian Andrzej Siewior
2021-01-25  8:30   ` Christoph Hellwig
2021-01-25  8:32     ` Sebastian Andrzej Siewior
2021-01-25  8:39       ` Christoph Hellwig
2021-01-25  9:54         ` [PATCH 3/3 v2] " Sebastian Andrzej Siewior
2021-01-25 10:14           ` Christoph Hellwig
2021-01-27 11:23           ` Daniel Wagner [this message]
2021-01-25  4:27 ` [PATCH v3 0/3] blk-mq: Don't complete in IRQ, use llist_head Jens Axboe
2021-02-10 14:43 ` Jens Axboe

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