From 78e05b1421fa41ae8457701140933baa5e7d9479 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Thu, 7 Aug 2014 15:36:18 +1000 Subject: [PATCH] powerpc: Add smp_mb()s to arch_spin_unlock_wait() Similar to the previous commit which described why we need to add a barrier to arch_spin_is_locked(), we have a similar problem with spin_unlock_wait(). We need a barrier on entry to ensure any spinlock we have previously taken is visibly locked prior to the load of lock->slock. It's also not clear if spin_unlock_wait() is intended to have ACQUIRE semantics. For now be conservative and add a barrier on exit to give it ACQUIRE semantics. Signed-off-by: Michael Ellerman Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/lib/locks.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c index 0c9c8d7..170a034 100644 --- a/arch/powerpc/lib/locks.c +++ b/arch/powerpc/lib/locks.c @@ -70,12 +70,16 @@ void __rw_yield(arch_rwlock_t *rw) void arch_spin_unlock_wait(arch_spinlock_t *lock) { + smp_mb(); + while (lock->slock) { HMT_low(); if (SHARED_PROCESSOR) __spin_yield(lock); } HMT_medium(); + + smp_mb(); } EXPORT_SYMBOL(arch_spin_unlock_wait); -- 2.7.4