Andrea Parri 472e8c55cf 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>		2018-02-23 08:38:16 +01:00
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asm	locking/xchg/alpha: Fix xchg() and cmpxchg() memory ordering bugs	2018-02-23 08:38:16 +01:00
uapi/asm	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mattst88/alpha	2018-02-02 13:46:21 -08:00