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From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>,
	Mike Snitzer <snitzer@redhat.com>,
	Alasdair Kergon <agk@redhat.com>, Ingo Molnar <mingo@kernel.org>,
	linux-kernel@vger.kernel.org, dm-devel@redhat.com,
	Joe Thornber <ejt@redhat.com>
Subject: Re: [RFC][PATCH] dm: Remove dm_bufio_cond_resched()
Date: Fri, 23 Sep 2016 11:13:22 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1609231111010.5640@nanos> (raw)
In-Reply-To: <20160923090524.GE5008@twins.programming.kicks-ass.net>

On Fri, 23 Sep 2016, Peter Zijlstra wrote:
> On Fri, Sep 23, 2016 at 10:00:37AM +0200, Thomas Gleixner wrote:
> > On Fri, 23 Sep 2016, Peter Zijlstra wrote:
> > > It is, might_sleep() implies might_resched(). In fact, that's all what
> > > PREEMPT_VOLUNTARY is, make the might_sleep() debug test imply a resched
> > > point.
> > 
> > Grr, how intuitive - NOT!
> 
> No, it actually makes sense. Because you 'obviously' only call
> might_sleep() in contexts that should be able to sleep (if not, it'll
> holler). So they're already placed right for preemption.

I disagree. might_sleep() is commonly known as a debug mechanism and it
existed before the preemption stuff went in. So the easy way to sprinkle
preemption points into the kernel was to hijack might_sleep(). I know it's
historical, but that doesnt make it any more intuitive.

Thanks,

	tglx

  reply	other threads:[~2016-09-23  9:16 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-13  8:45 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 [this message]
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
2016-09-19  9:49 ` Mikulas Patocka
2016-09-19 10:47   ` Peter Zijlstra

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