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authorMichael Ellerman <mpe@ellerman.id.au>2014-08-07 15:36:18 +1000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-10-05 14:52:21 -0700
commitafb3378f30b6fe6079d04c84052c7308661c27a9 (patch)
tree538558e0fe92bdd118aeccfe3b34b88df292db1c
parent4d4626b1fd183208b8f3e844964fc6b61625c90d (diff)
powerpc: Add smp_mb()s to arch_spin_unlock_wait()
commit 78e05b1421fa41ae8457701140933baa5e7d9479 upstream. 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 <mpe@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/powerpc/lib/locks.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
index 0c9c8d7d0734..170a0346f756 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);