From e0af21c56ddd592b33f74f986a2cb4478b10786e Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Fri, 11 Sep 2015 16:09:56 +0200 Subject: [PATCH] s390/spinlock: use correct barriers _raw_write_lock_wait first sets the high order bit to indicate a pending writer and then waits for the reader to drop to zero. smp_rmb by definition only orders reads against reads. Let's use a full smp_mb instead. As right now smp_rmb is implemented as full serialization, this needs no stable backport, but this patch will be necessary if we reimplement smp_rmb. Signed-off-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky --- arch/s390/lib/spinlock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c index d6c9991f7797..427aa44b3505 100644 --- a/arch/s390/lib/spinlock.c +++ b/arch/s390/lib/spinlock.c @@ -197,7 +197,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev) } old = ACCESS_ONCE(rw->lock); owner = ACCESS_ONCE(rw->owner); - smp_rmb(); + smp_mb(); if ((int) old >= 0) { prev = __RAW_LOCK(&rw->lock, 0x80000000, __RAW_OP_OR); old = prev; @@ -231,7 +231,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw) _raw_compare_and_swap(&rw->lock, old, old | 0x80000000)) prev = old; else - smp_rmb(); + smp_mb(); if ((old & 0x7fffffff) == 0 && (int) prev >= 0) break; if (MACHINE_HAS_CAD) -- 2.30.2