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s390/spinlock: use correct barriers

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_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 <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Christian Borntraeger 2015-09-11 16:09:56 +02:00 committed by Martin Schwidefsky
parent 9a21268360
commit e0af21c56d
1 changed files with 2 additions and 2 deletions
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4
arch/s390/lib/spinlock.c
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@ -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;
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