diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2017-10-23 14:07:22 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-10-25 11:01:03 +0200 |
| commit | c95491ed6d6a958743d82bea1d053819988da418 (patch) | |
| tree | ed32bc559c21b02396d11aafa41caef2e6b1aa1d /kernel/workqueue.c | |
| parent | 564cbc87937d5de1b5b666b0ed68122d6c74fa07 (diff) | |
locking/atomics, workqueue: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.
However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.
It's possible to transform the bulk of kernel code using the Coccinelle
script below. However, this doesn't handle comments, leaving references
to ACCESS_ONCE() instances which have been removed. As a preparatory
step, this patch converts the workqueue code and comments to use
{READ,WRITE}_ONCE() consistently.
----
virtual patch
@ depends on patch @
expression E1, E2;
@@
- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)
@ depends on patch @
expression E;
@@
- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-12-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 64d0edf428f8..39831b2f3c5f 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -4647,7 +4647,7 @@ static void rebind_workers(struct worker_pool *pool) * concurrency management. Note that when or whether * @worker clears REBOUND doesn't affect correctness. * - * ACCESS_ONCE() is necessary because @worker->flags may be + * WRITE_ONCE() is necessary because @worker->flags may be * tested without holding any lock in * wq_worker_waking_up(). Without it, NOT_RUNNING test may * fail incorrectly leading to premature concurrency @@ -4656,7 +4656,7 @@ static void rebind_workers(struct worker_pool *pool) WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND)); worker_flags |= WORKER_REBOUND; worker_flags &= ~WORKER_UNBOUND; - ACCESS_ONCE(worker->flags) = worker_flags; + WRITE_ONCE(worker->flags, worker_flags); } spin_unlock_irq(&pool->lock); |