Commit e0af21c5 authored Sep 11, 2015 by Christian Borntraeger Committed by Martin Schwidefsky Oct 14, 2015

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 <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

parent 9a212683

arch/s390/lib/spinlock.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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)