From: Christoph Hellwig <hch@infradead.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>,
frederic@kernel.org, linux-kernel@vger.kernel.org,
linux-block@vger.kernel.org
Subject: Re: blk-softirq vs smp_call_function_single_async()
Date: Mon, 8 Jun 2020 08:45:57 -0700 [thread overview]
Message-ID: <20200608154557.GA26611@infradead.org> (raw)
In-Reply-To: <20200608115800.GA2531@hirez.programming.kicks-ass.net>
On Mon, Jun 08, 2020 at 01:58:00PM +0200, Peter Zijlstra wrote:
> Hi Jens,
>
> I've been going through smp_call_function_single_async() users and
> stumbled upon blk-softirq.c, which has:
>
> static int raise_blk_irq(int cpu, struct request *rq)
> {
> if (cpu_online(cpu)) {
> call_single_data_t *data = &rq->csd;
>
> data->func = trigger_softirq;
> data->info = rq;
> data->flags = 0;
>
> smp_call_function_single_async(cpu, data);
> return 0;
> }
>
> return 1;
> }
>
> What, if anything, guarantees rq->csd is not already in use at that
> time?
A request can only be completed once.
next prev parent reply other threads:[~2020-06-08 15:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-08 11:58 blk-softirq vs smp_call_function_single_async() Peter Zijlstra
2020-06-08 15:45 ` Christoph Hellwig [this message]
2020-06-08 15:58 ` Peter Zijlstra
2020-06-08 16:33 ` Christoph Hellwig
2020-06-08 16:40 ` Peter Zijlstra
2020-06-08 16:42 ` Christoph Hellwig
2020-06-09 13:38 ` Peter Zijlstra
2020-06-08 21:34 ` Jens Axboe
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