[tip:locking/core] locking/core, s390: Make cpu_relax() a barrier again

From: tip-bot for Christian Borntraeger
Date: Wed Nov 16 2016 - 07:11:50 EST

Commit-ID: 22b6430d36659b37ed139b7fd87fcc7237fb0cfd
Gitweb: http://git.kernel.org/tip/22b6430d36659b37ed139b7fd87fcc7237fb0cfd
Author: Christian Borntraeger <borntraeger@xxxxxxxxxx>
AuthorDate: Tue, 25 Oct 2016 11:03:13 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 16 Nov 2016 10:15:10 +0100

locking/core, s390: Make cpu_relax() a barrier again

stop_machine() seemed to be the only important place for yielding during
cpu_relax(). This was fixed by using cpu_relax_yield().

Therefore, we can now redefine cpu_relax() to be a barrier instead on s390,
making s390 identical to all other architectures.

Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Noam Camus <noamc@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1477386195-32736-4-git-send-email-borntraeger@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
arch/s390/include/asm/processor.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 5bb4433..79343e3 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -236,7 +236,7 @@ static inline unsigned short stap(void)
void cpu_relax_yield(void);

-#define cpu_relax() cpu_relax_yield()
+#define cpu_relax() barrier()
#define cpu_relax_lowlatency() barrier()