From: Peter Zijlstra <peterz@infradead.org>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>,
Mike Snitzer <snitzer@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel@vger.kernel.org, dm-devel@redhat.com
Subject: Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched()
Date: Mon, 19 Sep 2016 12:47:52 +0200 [thread overview]
Message-ID: <20160919104752.GV5016@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.LRH.2.02.1609190542150.15526@file01.intranet.prod.int.rdu2.redhat.com>
On Mon, Sep 19, 2016 at 05:49:07AM -0400, Mikulas Patocka wrote:
>
>
> On Tue, 13 Sep 2016, Peter Zijlstra wrote:
>
> > Hi all,
> >
> > While grepping for PREEMPT_VOLUNTARY I ran into dm_bufio_cond_resched()
> > and wondered WTH it was about.
>
> cond_resched() calls _cond_resched() even if when we have a preemptive
> kernel - with preemptive kernel, calling cond_resched is pointless because
> rescheduling is done peemtively.
>
> So, I added that dm_bufio_cond_resched(), that does nothing on peemptive
> kernels (and also on PREEMPT_NONE kernels where the user doesn't care
> about latency).
>
> What is the reason why cond_resched() tests for rescheduling with
> preemptive kernel? Why should I use cond_resched() in that case?
Because every body else does too. 'Fixing' something like that in the dm
code is entirely the wrong place. Also, you loose out on the
might_sleep() warning implied in it.
As it happens, I have a patch fixing that somewhere, let me try and get
it merged.
But thanks for the reminder, I'll go write a Changelog for this so that
people can commit.
prev parent reply other threads:[~2016-09-19 10:48 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-13 8:45 [RFC][PATCH] dm: Remove dm_bufio_cond_resched() Peter Zijlstra
2016-09-13 12:49 ` Thomas Gleixner
2016-09-13 13:39 ` Mike Snitzer
2016-09-19 10:53 ` Peter Zijlstra
2016-09-22 20:53 ` Mikulas Patocka
2016-09-22 20:59 ` Thomas Gleixner
2016-09-23 7:34 ` Peter Zijlstra
2016-09-23 8:00 ` Thomas Gleixner
2016-09-23 9:05 ` Peter Zijlstra
2016-09-23 9:13 ` Thomas Gleixner
2016-09-23 9:26 ` Ingo Molnar
2016-09-23 12:17 ` Mike Galbraith
2016-09-23 12:26 ` Peter Zijlstra
2016-09-23 12:39 ` Mike Galbraith
2016-09-23 12:42 ` Mike Snitzer
2016-09-23 12:46 ` Peter Zijlstra
2016-09-23 14:32 ` [dm-devel] " Bart Van Assche
2016-09-23 14:32 ` Bart Van Assche
2016-09-19 9:49 ` Mikulas Patocka
2016-09-19 10:47 ` Peter Zijlstra [this message]
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