linux-kernel - Re: [PATCH] tick-sched: avoid a maybe-uninitialized warning

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Message-ID: <2227858.przuGYB40B@aspire.rjw.lan>
Date:   Tue, 10 Apr 2018 09:16:49 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...nel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tick-sched: avoid a maybe-uninitialized warning

On Monday, April 9, 2018 7:53:30 PM CEST Arnd Bergmann wrote:
> On Mon, Apr 9, 2018 at 6:18 PM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Arnd Bergmann <arnd@...db.de> wrote:
> >
> >> The use of bitfields seems to confuse gcc, leading to a false-positive
> >> warning in all compiler versions:
> >>
> >> kernel/time/tick-sched.c: In function 'tick_nohz_idle_exit':
> >> kernel/time/tick-sched.c:538:2: error: 'now' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> >>
> >> This introduces a temporary variable to track the flags so gcc
> >> doesn't have to evaluate twice, eliminating the code path that
> >> leads to the warning.
> >>
> >> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85301
> >> Fixes: 1cae544d42d2 ("nohz: Gather tick_sched booleans under a common flag field")
> >> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> >
> > Which tree is this against? There's no such commit either in -tip, upstream or in
> > -next AFAICS.
> 
> It's in today's linux-next. I found that it came in through Rafael's
> pm/linux-next tree.

That's the idle loop rework series.

I'll add this patch on top of that if there are no objections.

Thanks,
Rafael