linux-kernel - Re: [PATCH 06/10] posix-cpu-timers: fix wrong timer initialization

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Date:	Tue, 30 Apr 2013 09:34:54 -0400
From:	Olivier Langlois <olivier@...llion01.com>
To:	kosaki.motohiro@...il.com
Cc:	linux-kernel@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	David Miller <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [PATCH 06/10] posix-cpu-timers: fix wrong timer initialization

On Mon, 2013-04-29 at 23:17 -0400, kosaki.motohiro@...il.com wrote:
> From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> 
> Currently glibc's rt/tst-cputimer1 testcase is spradically fail because
> a timer created by timer_create() may fire earlier than it's specified.
> 
> posix_cpu_timer_set() uses "val" as current time for three purpose. 1)
> initialize sig->cputimer. 2) calculation "old" val. 3) calculations an
> expires time.
> 
> (1) and (2) should be used only committed time (i.e. without delta_exec)
> because run_posix_cpu_timers() don't care of delta_exec and we need
> consistency. But (3) need exact current time (aka cpu clock time) beucase
> an expires should be "now + timeout" by definition.
> 
> This patch makes separete two kind of "now".
> 
Kosaki,

I must admit that this solution is simpler to what I originally
proposed.

good work!
Olivier



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