From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: David Runge <dave@sleepmap.de>,
linux-rt-users@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Daniel Wagner <dwagner@suse.de>
Subject: Re: [PATCH RFC] blk-mq: Don't IPI requests on PREEMPT_RT
Date: Fri, 23 Oct 2020 15:52:19 +0200 [thread overview]
Message-ID: <20201023135219.mzzl76eqqy6tqwhe@linutronix.de> (raw)
In-Reply-To: <20201023112130.GA23790@infradead.org>
On 2020-10-23 12:21:30 [+0100], Christoph Hellwig wrote:
> > - if (!IS_ENABLED(CONFIG_SMP) ||
> > + if (!IS_ENABLED(CONFIG_SMP) || IS_ENABLED(CONFIG_PREEMPT_RT) ||
> > !test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags))
>
> This needs a big fat comment explaining your rationale. And probably
> a separate if statement to make it obvious as well.
Okay.
How much difference does it make between completing in-softirq vs
in-IPI? I'm asking because acquiring a spinlock_t in an IPI shouldn't be
done (as per Documentation/locking/locktypes.rst). We don't have
anything in lockdep that will complain here on !RT and we the above we
avoid the case on RT.
Sebastian
next prev parent reply other threads:[~2020-10-23 13:52 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201021175059.GA4989@hmbx>
2020-10-23 11:04 ` [PATCH RFC] blk-mq: Don't IPI requests on PREEMPT_RT Sebastian Andrzej Siewior
2020-10-23 11:21 ` Christoph Hellwig
2020-10-23 13:52 ` Sebastian Andrzej Siewior [this message]
2020-10-27 9:26 ` Christoph Hellwig
2020-10-27 10:11 ` Sebastian Andrzej Siewior
2020-10-27 16:07 ` Christoph Hellwig
2020-10-27 17:05 ` Thomas Gleixner
2020-10-27 17:23 ` Christoph Hellwig
2020-10-27 17:59 ` Sebastian Andrzej Siewior
2020-10-27 20:58 ` Sebastian Andrzej Siewior
2020-10-28 6:56 ` Christoph Hellwig
2020-10-28 14:12 ` [PATCH 1/3] blk-mq: Don't complete on a remote CPU in force threaded mode Sebastian Andrzej Siewior
2020-10-28 14:12 ` [PATCH 2/3] blk-mq: Always complete remote completions requests in softirq Sebastian Andrzej Siewior
2020-10-28 14:12 ` [PATCH 3/3] blk-mq: Use llist_head for blk_cpu_done Sebastian Andrzej Siewior
2020-10-28 14:44 ` Christoph Hellwig
2020-10-28 14:47 ` Sebastian Andrzej Siewior
2020-10-29 13:12 ` Sebastian Andrzej Siewior
2020-10-29 14:05 ` Christoph Hellwig
2020-10-29 14:56 ` Sebastian Andrzej Siewior
2020-10-29 14:57 ` Christoph Hellwig
2020-10-29 20:03 ` Sagi Grimberg
2020-10-29 21:01 ` Sebastian Andrzej Siewior
2020-10-29 21:07 ` Sagi Grimberg
2020-10-31 10:41 ` Sebastian Andrzej Siewior
2020-10-31 15:00 ` Jens Axboe
2020-10-31 15:01 ` Jens Axboe
2020-10-31 18:09 ` Christoph Hellwig
2020-11-02 9:55 ` Sebastian Andrzej Siewior
2020-11-02 18:12 ` Christoph Hellwig
2020-11-04 19:15 ` Sagi Grimberg
2020-11-06 15:23 ` Sebastian Andrzej Siewior
2020-10-28 10:04 ` [PATCH RFC] blk-mq: Don't IPI requests on PREEMPT_RT Peter Zijlstra
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