rcu: Make arch select smp_mb__after_unlock_lock() strength
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Sat, 14 Jan 2017 21:32:50 +0000 (13:32 -0800)
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tue, 18 Apr 2017 18:20:15 +0000 (11:20 -0700)
commit77e5849688670280b173bb9e0544e9da7b2acc36
tree7d1bab5108080b74bca1c7a8d54e3be22c67c6e2
parentb8c17e6664c461e4aed545a943304c3b32dd309c
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: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul 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: Michael Ellerman <mpe@ellerman.id.au>
Cc: <linuxppc-dev@lists.ozlabs.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
arch/Kconfig
arch/powerpc/Kconfig
include/linux/rcupdate.h