Commit-ID: 548095dea63ffc016d39c35b32c628d033638aca
Gitweb: https://git.kernel.org/tip/548095dea63ffc016d39c35b32c628d033638aca
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 9 Oct 2017 11:22:50 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 4 Dec 2017 10:52:55 -0800
locking: Remove smp_read_barrier_depends() from queued_spin_lock_slowpath()
Queued spinlocks are not used by DEC Alpha, and furthermore operations
such as READ_ONCE() and release/relaxed RMW atomics are being changed
to imply smp_read_barrier_depends(). This commit therefore removes the
now-redundant smp_read_barrier_depends() from queued_spin_lock_slowpath(),
and adjusts the comments accordingly.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/locking/qspinlock.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 294294c..38ece03 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -170,7 +170,7 @@ static __always_inline void clear_pending_set_locked(struct qspinlock *lock)
* @tail : The new queue tail code word
* Return: The previous queue tail code word
*
- * xchg(lock, tail)
+ * xchg(lock, tail), which heads an address dependency
*
* p,*,* -> n,*,* ; prev = xchg(lock, node)
*/
@@ -409,13 +409,11 @@ queue:
if (old & _Q_TAIL_MASK) {
prev = decode_tail(old);
/*
- * The above xchg_tail() is also a load of @lock which generates,
- * through decode_tail(), a pointer.
- *
- * The address dependency matches the RELEASE of xchg_tail()
- * such that the access to @prev must happen after.
+ * The above xchg_tail() is also a load of @lock which
+ * generates, through decode_tail(), a pointer. The address
+ * dependency matches the RELEASE of xchg_tail() such that
+ * the subsequent access to @prev happens after.
*/
- smp_read_barrier_depends();
WRITE_ONCE(prev->next, node);
--
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