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| author |   Andrea Parri <parri.andrea@gmail.com> | 2018-02-22 10:24:48 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2018-02-23 08:38:16 +0100 |
| commit | 472e8c55cf6622d1c112dc2bc777f68bbd4189db (patch) | |
| tree | 8f91fed0fa1000eef3790b086903b6409ba50358 /include | |
| parent | locking/xchg/alpha: Clean up barrier usage by using smp_mb() in place of __ASM__MB (diff) | |
| download | linux-dev-472e8c55cf6622d1c112dc2bc777f68bbd4189db.tar.xz linux-dev-472e8c55cf6622d1c112dc2bc777f68bbd4189db.zip | |
locking/xchg/alpha: Fix xchg() and cmpxchg() memory ordering bugs
Successful RMW operations are supposed to be fully ordered, but
Alpha's xchg() and cmpxchg() do not meet this requirement.
Will Deacon noticed the bug:
> So MP using xchg:
>
> WRITE_ONCE(x, 1)
> xchg(y, 1)
>
> smp_load_acquire(y) == 1
> READ_ONCE(x) == 0
>
> would be allowed.
... which thus violates the above requirement.
Fix it by adding a leading smp_mb() to the xchg() and cmpxchg() implementations.
Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-alpha@vger.kernel.org
Link: http://lkml.kernel.org/r/1519291488-5752-1-git-send-email-parri.andrea@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include')
0 files changed, 0 insertions, 0 deletions