linux-kernel - Re: [PATCH 0/6] sched, wait: Collapse __wait

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Date:	Tue, 1 Oct 2013 17:16:38 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/6] sched, wait: Collapse __wait_event macros -v4

On 10/01, Peter Zijlstra wrote:
>
> On Tue, Oct 01, 2013 at 04:09:40PM +0200, Oleg Nesterov wrote:
> > But somehow I didn't realize that ___wait_cond_timeout() can be used
> > as is, so the simple patch below should work?
>
> Yeah, should work.. But how often do people use timeout=0?

I do not know. Perhaps never.

> Should we
> really care about that case to the effect of adding more code.

Again, I do not really know. But imo it would be better to fix
this anyway, even if the problem is really minor. If nothing
else, wait_event_timeout() and __wait_event_timeout() should have
the same semantics.

And suppose that we ha a helper(timeout) which calls wait_event_timeout(),
and checks the non-trivial condition inside. Now suppose that someone
does

	timeout = DEFAULT_TIMEOUT;

	if (option_nonblock)
		timeout = 0;

	ok = helper(timeout);

So do you think we should ignore this or I should send 7/6 with the
changelog ?

(In fact I am going to send another patch on top of this series later.
 At least, try to send for discussion because I know you dislike the
 idea to move the signal-pending checks out of line).

Oleg.

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