diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2018-12-18 23:10:40 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-12-21 14:11:33 +0100 |
| commit | c3b6e79fbf295c9cda4dd1828a8f0593cad53d48 (patch) | |
| tree | 698fd5c530c07fef83f3457a1340b9f6dd16f299 /kernel | |
| parent | d395117fac7943da6966ccbac3b95651f5581f15 (diff) | |
locking: Remove smp_read_barrier_depends() from queued_spin_lock_slowpath()
commit 548095dea63ffc016d39c35b32c628d033638aca upstream.
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@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/locking/qspinlock.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index a72f5df643f8..8710fbe8d26c 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -169,7 +169,7 @@ 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) */ @@ -533,13 +533,11 @@ 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); |