From: Manfred Spraul <manfred@colorfullife.com>
To: Arnd Bergmann <arnd@arndb.de>, "kernelci.org bot" <bot@kernelci.org>
Cc: Kernel Build Reports Mailman List
<kernel-build-reports@lists.linaro.org>,
"3.16.x" <stable@vger.kernel.org>,
Ben Hutchings <ben@decadent.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: stable/linux-3.16.y build: 178 builds: 1 failed, 177 passed, 2 errors, 57 warnings (v3.16.52)
Date: Sat, 13 Jan 2018 19:51:06 +0100 [thread overview]
Message-ID: <0ecf39a8-dfc1-e895-ad6b-e2cf21a30e01@colorfullife.com> (raw)
In-Reply-To: <CAK8P3a1ffauonXr-ew5Y2kkn8qkFE1N27xJtnD4UaJmj+y1hwg@mail.gmail.com>
Hi Arnd,
On 01/03/2018 12:15 AM, Arnd Bergmann wrote:
>
>> 2 ipc/sem.c:377:6: warning: '___p1' may be used uninitialized in this function [-Wmaybe-uninitialized]
> This code was last touched in 3.16 by the backport of commit
> 5864a2fd3088 ("ipc/sem.c: fix complex_count vs. simple op race")
>
> The warning is in "smp_load_acquire(&sma->complex_mode))", and I suspect
> that commit 27d7be1801a4 ("ipc/sem.c: avoid using spin_unlock_wait()")
> avoided the warning upstream by removing the smp_mb() before it.
The smp_mb() pairs with spin_unlock_wait() in complexmode_enter()
It is removed by commit 27d7be1801a4 ("ipc/sem.c: avoid using
spin_unlock_wait()").
From what I see, it doesn't exist in any of the stable kernels
(intentionally, the above commit is a rewrite for better performance).
___p1 is from smp_load_acquire()
> typeof(*p) ___p1 = READ_ONCE(*p); \
I don't see how ___p1 could be used uninitialized. Perhaps a compiler issue?
--
Manfred
next prev parent reply other threads:[~2018-01-13 18:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <5a4b7192.08f4500a.dd9fa.064c@mx.google.com>
2018-01-02 23:15 ` stable/linux-3.16.y build: 178 builds: 1 failed, 177 passed, 2 errors, 57 warnings (v3.16.52) Arnd Bergmann
2018-01-13 18:51 ` Manfred Spraul [this message]
2018-11-11 1:47 ` Ben Hutchings
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