linux-kernel - Re: [PATCH 1/9] sched: add schedule_timeout

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Message-ID: <20160322212352.GF6356@twins.programming.kicks-ass.net>
Date:	Tue, 22 Mar 2016 22:23:52 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Michal Hocko <mhocko@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	David Rientjes <rientjes@...gle.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/9] sched: add schedule_timeout_idle()

On Tue, Mar 22, 2016 at 01:56:26PM -0400, Johannes Weiner wrote:
> On Tue, Mar 22, 2016 at 02:22:49PM +0100, Peter Zijlstra wrote:
> > On Tue, Mar 22, 2016 at 02:08:23PM +0100, Michal Hocko wrote:
> > > On Tue 22-03-16 13:51:13, Peter Zijlstra wrote:
> > > If that sounds like a more appropriate plan I won't object. I can simply
> > > change my patch to do __set_current_state and schedule_timeout.
> > 
> > I dunno, I just think these wrappers are silly.
> 
> Adding out-of-line, exported wrappers for every single task state is
> kind of silly. But it's still a common operation to wait in a certain
> state, so having a single function for that makes sense. Kind of like
> spin_lock_irqsave and friends.
> 
> Maybe this would be better?:
> 
> static inline long schedule_timeout_state(long timeout, long state)
> {
> 	__set_current_state(state);
> 	return schedule_timeout(timeout);
> }

Probably. However, with such semantics the schedule*() name is wrong
too, you cannot use these functions to build actual wait loops etc.

So maybe:

static inline long sleep_in_state(long timeout, long state)
{
	__set_current_state(state);
	return schedule_timeout(timeout);
}

might be an even better name; but at that point we look very like the
msleep*() class of function, so maybe we should do:

long sleep_in_state(long state, long timeout)
{
	while (timeout && !signal_pending_state(state, current)) {
		__set_current_state(state);
		timeout = schedule_timeout(timeout);
	}
	return timeout;
}

Hmm ?