[PATCH 3/6] workqueue: release pwq pools by pool type

[Breno Leitao <leitao@debian.org>]

pwq_release_workfn() calls put_unbound_pool() based on the WQ_UNBOUND
flag. That works today because an unbound workqueue only ever points at
unbound pools, but the flag is the wrong thing to test: what matters is
whether the pool is a refcounted unbound pool or a permanent per-cpu one.

Add is_pool_cpu_specific() and key the release on it instead of the flag.
This is equivalent for every existing workqueue and stays correct if an
unbound pwq is ever backed by a per-cpu pool. Convert the other
open-coded pool->cpu type checks -- in put_unbound_pool(),
pool_allowed_cpus() and the workqueue watchdog -- to the same helper.

No functional change.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 kernel/workqueue.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index b386a457c0381..513193be00a7d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1604,6 +1604,12 @@ work_func_t wq_worker_last_func(struct task_struct *task)
 	return worker->last_func;
 }
 
+/* True if @pool is tied to a specific CPU, rather than an unbound pool. */
+static bool is_pool_cpu_specific(struct worker_pool *pool)
+{
+	return pool->cpu >= 0;
+}
+
 /**
  * wq_node_nr_active - Determine wq_node_nr_active to use
  * @wq: workqueue of interest
@@ -2753,7 +2759,7 @@ static struct worker *alloc_worker(int node)
 
 static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
 {
-	if (pool->cpu < 0 && pool->attrs->affn_strict)
+	if (!is_pool_cpu_specific(pool) && pool->attrs->affn_strict)
 		return pool->attrs->__pod_cpumask;
 	else
 		return pool->attrs->cpumask;
@@ -5121,7 +5127,7 @@ static void put_unbound_pool(struct worker_pool *pool)
 		return;
 
 	/* sanity checks */
-	if (WARN_ON(!(pool->cpu < 0)) ||
+	if (WARN_ON(is_pool_cpu_specific(pool)) ||
 	    WARN_ON(!list_empty(&pool->worklist)))
 		return;
 
@@ -5273,7 +5279,7 @@ static void pwq_release_workfn(struct kthread_work *work)
 		mutex_unlock(&wq->mutex);
 	}
 
-	if (wq->flags & WQ_UNBOUND) {
+	if (!is_pool_cpu_specific(pool)) {
 		mutex_lock(&wq_pool_mutex);
 		put_unbound_pool(pool);
 		mutex_unlock(&wq_pool_mutex);
@@ -7949,7 +7955,7 @@ static void wq_watchdog_timer_fn(struct timer_list *unused)
 			lockup_detected = true;
 			stall_time = jiffies_to_msecs(now - pool_ts) / 1000;
 			max_stall_time = max(max_stall_time, stall_time);
-			if (pool->cpu >= 0 && !(pool->flags & POOL_BH)) {
+			if (is_pool_cpu_specific(pool) && !(pool->flags & POOL_BH)) {
 				pool->cpu_stall = true;
 				cpu_pool_stall = true;
 			}

-- 
2.53.0-Meta