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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-10-09 21:22:50 +0300 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-12-04 21:52:55 +0300 |
commit | 548095dea63ffc016d39c35b32c628d033638aca (patch) | |
tree | 33c562914bcb3f6d3441afc961c1007e89c769f4 | |
parent | 5c6338b4877038d28148fcfe1e7f862970ebaad1 (diff) | |
download | linux-548095dea63ffc016d39c35b32c628d033638aca.tar.xz |
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@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
-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 294294c71ba4..38ece035039e 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); |