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
But thanks for the reminder, I'll go write a Changelog for this so that
people can commit.
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