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Commit 77e58496 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Make arch select smp_mb__after_unlock_lock() strength 



The definition of smp_mb__after_unlock_lock() is currently smp_mb()
for CONFIG_PPC and a no-op otherwise.  It would be better to instead
provide an architecture-selectable Kconfig option, and select the
strength of smp_mb__after_unlock_lock() based on that option.  This
commit therefore creates ARCH_WEAK_RELEASE_ACQUIRE, has PPC select it,
and bases the definition of smp_mb__after_unlock_lock() on this new
ARCH_WEAK_RELEASE_ACQUIRE Kconfig option.

Reported-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Boqun Feng <boqun.feng@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Cc: <linuxppc-dev@lists.ozlabs.org>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent b8c17e66

arch/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -320,6 +320,9 @@ config HAVE_CMPXCHG_LOCAL 
config HAVE_CMPXCHG_DOUBLE

	bool



config ARCH_WEAK_RELEASE_ACQUIRE

	bool



config ARCH_WANT_IPC_PARSE_VERSION

	bool

arch/powerpc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -99,6 +99,7 @@ config PPC 
	select ARCH_USE_BUILTIN_BSWAP

	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64

	select ARCH_WANT_IPC_PARSE_VERSION

	select ARCH_WEAK_RELEASE_ACQUIRE

	select BINFMT_ELF

	select BUILDTIME_EXTABLE_SORT

	select CLONE_BACKWARDS

include/linux/rcupdate.h

+3 −3
Original line number Diff line number Diff line
@@ -1127,11 +1127,11 @@ do { \ 
 * if the UNLOCK and LOCK are executed by the same CPU or if the

 * UNLOCK and LOCK operate on the same lock variable.

 */

#ifdef CONFIG_PPC

#ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE

#define smp_mb__after_unlock_lock()	smp_mb()  /* Full ordering for lock. */

#else /* #ifdef CONFIG_PPC */

#else /* #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */

#define smp_mb__after_unlock_lock()	do { } while (0)

#endif /* #else #ifdef CONFIG_PPC */

#endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */





#endif /* __LINUX_RCUPDATE_H */