[PATCH 2/7 V2] workqueue: simplify wq_update_unbound_numa()

From: Lai Jiangshan
Date: Tue May 12 2015 - 08:30:31 EST


wq_update_unbound_numa() is known be called with wq_pool_mutex held.

But wq_update_unbound_numa() requests wq->mutex before reading
wq->unbound_attrs, wq->numa_pwq_tbl[] and wq->dfl_pwq. But these fields
were changed to be allowed being read with wq_pool_mutex held. So we
simply remove the mutex_lock(&wq->mutex).

Without the dependence on the the mutex_lock(&wq->mutex), the test
of wq->unbound_attrs->no_numa can also be moved upward.

The old code need a long comment to describe the stableness of
@wq->unbound_attrs which is also guaranteed by wq_pool_mutex now,
so we don't need this such comment.

Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
---
kernel/workqueue.c | 20 +++++---------------
1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f02b8ad..c8b9de0 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3708,7 +3708,8 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,

lockdep_assert_held(&wq_pool_mutex);

- if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND))
+ if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
+ wq->unbound_attrs->no_numa)
return;

/*
@@ -3719,10 +3720,6 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
target_attrs = wq_update_unbound_numa_attrs_buf;
cpumask = target_attrs->cpumask;

- mutex_lock(&wq->mutex);
- if (wq->unbound_attrs->no_numa)
- goto out_unlock;
-
copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
pwq = unbound_pwq_by_node(wq, node);

@@ -3734,33 +3731,26 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
*/
if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
- goto out_unlock;
+ return;
} else {
goto use_dfl_pwq;
}

- mutex_unlock(&wq->mutex);
-
/* create a new pwq */
pwq = alloc_unbound_pwq(wq, target_attrs);
if (!pwq) {
pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
wq->name);
- mutex_lock(&wq->mutex);
goto use_dfl_pwq;
}

- /*
- * Install the new pwq. As this function is called only from CPU
- * hotplug callbacks and applying a new attrs is wrapped with
- * get/put_online_cpus(), @wq->unbound_attrs couldn't have changed
- * inbetween.
- */
+ /* Install the new pwq. */
mutex_lock(&wq->mutex);
old_pwq = numa_pwq_tbl_install(wq, node, pwq);
goto out_unlock;

use_dfl_pwq:
+ mutex_lock(&wq->mutex);
spin_lock_irq(&wq->dfl_pwq->pool->lock);
get_pwq(wq->dfl_pwq);
spin_unlock_irq(&wq->dfl_pwq->pool->lock);
--
2.1.0

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