linux-kernel - Re: [PATCH 1/4] posix_cpu_timer: Consolidate expiry time type

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Message-ID: <CAFTL4hyOc62OJ6+-VRyLw8_6R4pWrNHw2k2y=U9HrAEKN8Zjww@mail.gmail.com>
Date:	Wed, 20 Mar 2013 01:25:22 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Stanislaw Gruszka <sgruszka@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 1/4] posix_cpu_timer: Consolidate expiry time type

2013/3/19 Andrew Morton <akpm@...ux-foundation.org>:
> On Fri, 15 Mar 2013 17:53:59 +0100 Frederic Weisbecker <fweisbec@...il.com> wrote:
>
>> The posix cpu timer expiry time is stored in a union of
>> two types: a 64 bits field if we rely on scheduler precise
>> accounting, or a cputime_t if we rely on jiffies.
>>
>> This result in quite some duplicate code and special cases
>> to handle the two types.
>>
>> Just unify this into a single 64 bits field. cputime_t can
>> always fit into it.
>>
>
> x86_64 allnoconfig:
>
> kernel/posix-cpu-timers.c: In function 'posix_cpu_timer_schedule':
> kernel/posix-cpu-timers.c:1127: warning: 'now' may be used uninitialized in this function
>
> It looks like it's always been buggy, but your switch from `union
> cou_time_count' to `unsigned long long' made gcc notice it.

Ok, from a quick view it seems what's missing is a call to
cpu_timer_sample_group() to compute the residual time for further call
of timer_gettime(). I'll look at it deeper and send you a fix.

Thanks.
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