From: "Paul E. McKenney" <paulmck@kernel.org>
To: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Linux Next Mailing List <linux-next@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>
Subject: Re: linux-next: build warning after merge of the rcu tree
Date: Wed, 11 Dec 2019 22:02:00 -0800 [thread overview]
Message-ID: <20191212060200.GW2889@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20191212160622.021517d3@canb.auug.org.au>
On Thu, Dec 12, 2019 at 04:06:22PM +1100, Stephen Rothwell wrote:
> Hi all,
>
> After merging the rcu (I think) tree, today's linux-next build (x86_64
> allnoconfig) produced this warning:
>
> kernel/time/timer.c: In function 'schedule_timeout':
> kernel/time/timer.c:969:20: warning: 'timer.expires' may be used uninitialized in this function [-Wmaybe-uninitialized]
> 969 | long diff = timer->expires - expires;
> | ~~~~~^~~~~~~~~
>
> Introduced by (bisected to) commit
>
> c4127fce1d02 ("timer: Use hlist_unhashed_lockless() in timer_pending()")
>
> x86_64-linux-gnu-gcc (Debian 9.2.1-21) 9.2.1 20191130
Well, if the timer is pending, then ->expires has to have been
initialized, but off where the compiler cannot see it, such as during a
previous call to __mod_timer(). And the change may have made it harder
for the compiler to see all of these relationships, but...
I don't see this warning with gcc version 7.4.0. Just out of curiosity,
what are you running, Stephen?
Eric, any thoughts for properly educating the compiler on this one?
Thanx, Paul
next prev parent reply other threads:[~2019-12-12 6:02 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 5:06 linux-next: build warning after merge of the rcu tree Stephen Rothwell
2019-12-12 6:02 ` Paul E. McKenney [this message]
2019-12-12 6:38 ` Eric Dumazet
2019-12-12 6:57 ` Eric Dumazet
2020-01-10 21:57 ` Paul E. McKenney
2020-01-15 16:42 ` Paul E. McKenney
2019-12-12 11:40 ` Stephen Rothwell
2019-12-13 1:31 ` Paul E. McKenney
2020-01-06 17:51 ` Olof Johansson
2020-01-06 18:10 ` Paul E. McKenney
2020-01-06 21:08 ` Olof Johansson
2020-01-06 21:43 ` Paul E. McKenney
-- strict thread matches above, loose matches on Subject: below --
2024-01-25 3:33 Stephen Rothwell
2024-01-25 13:18 ` Paul E. McKenney
2023-07-26 2:32 Stephen Rothwell
2023-07-26 3:33 ` Paul E. McKenney
2023-07-26 3:48 ` Paul E. McKenney
2023-07-26 6:37 ` Stephen Rothwell
2023-04-06 4:43 Stephen Rothwell
2023-04-06 14:15 ` Paul E. McKenney
2023-03-21 2:50 Stephen Rothwell
2023-03-21 3:01 ` Boqun Feng
2022-11-07 3:26 Stephen Rothwell
2022-11-07 5:02 ` Paul E. McKenney
2022-11-07 9:28 ` Akira Yokosawa
2022-06-15 5:38 Stephen Rothwell
2022-06-15 13:55 ` Paul E. McKenney
2021-03-04 1:41 Stephen Rothwell
2021-03-04 1:48 ` Paul E. McKenney
2020-12-07 8:20 Stephen Rothwell
2020-12-07 16:47 ` Paul E. McKenney
2020-12-07 17:48 ` Jonathan Corbet
2020-12-07 18:53 ` Paul E. McKenney
2020-03-10 2:27 Stephen Rothwell
2020-03-10 2:49 ` Paul E. McKenney
2017-06-21 6:48 Stephen Rothwell
2017-06-21 13:30 ` Paul E. McKenney
2011-08-24 4:23 Stephen Rothwell
2011-08-24 12:27 ` Paul E. McKenney
2011-08-25 0:46 ` Arnaud Lacombe
2011-08-25 5:04 ` Paul E. McKenney
2011-03-25 5:05 Stephen Rothwell
2011-03-25 19:23 ` Paul E. McKenney
2010-09-06 2:14 Stephen Rothwell
2010-09-06 2:32 ` Neil Brown
2010-09-06 3:02 ` Stephen Rothwell
2010-09-06 5:37 ` Paul E. McKenney
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