Messages in this thread | | | Subject | Re: stable/linux-3.16.y build: 178 builds: 1 failed, 177 passed, 2 errors, 57 warnings (v3.16.52) | From | Ben Hutchings <> | Date | Sun, 11 Nov 2018 01:47:27 +0000 |
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On Sat, 2018-01-13 at 19:51 +0100, Manfred Spraul wrote: > 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?
On arm64 smp_load_acquire() was implemented in assembly that only supported 4-byte and 8-byte words. And complex_mode is a bool (1-byte) field.
So I believe the fix is:
878a84d5a8a1 arm64: add missing data types in smp_load_acquire/smp_store_release
Ben.
-- Ben Hutchings Reality is just a crutch for people who can't handle science fiction.
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