[PATCH 6.7 087/713] workqueue: Make wq_adjust_max_active() round-robin pwqs while activating

Sasha Levin
2024-03-24T22:48:45Z

From: Tejun Heo <tj@kernel.org>

[ Upstream commit c5404d4e6df6faba1007544b5f4e62c7c14416dd ]

wq_adjust_max_active() needs to activate work items after max_active is
increased. Previously, it did that by visiting each pwq once activating all
that could be activated. While this makes sense with per-pwq nr_active,
nr_active will be shared across multiple pwqs for unbound wqs. Then, we'd
want to round-robin through pwqs to be fairer.

In preparation, this patch makes wq_adjust_max_active() round-robin pwqs
while activating. While the activation ordering changes, this shouldn't
cause user-noticeable behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Stable-dep-of: 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/workqueue.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 78b4f4e3e41dd..059f122563def 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4710,7 +4710,7 @@ static int init_rescuer(struct workqueue_struct *wq)
*/
static void wq_adjust_max_active(struct workqueue_struct *wq)
{
- struct pool_workqueue *pwq;
+ bool activated;

lockdep_assert_held(&wq->mutex);

@@ -4730,19 +4730,26 @@ static void wq_adjust_max_active(struct workqueue_struct *wq)
*/
WRITE_ONCE(wq->max_active, wq->saved_max_active);

- for_each_pwq(pwq, wq) {
- unsigned long flags;
-
- /* this function can be called during early boot w/ irq disabled */
- raw_spin_lock_irqsave(&pwq->pool->lock, flags);
-
- while (pwq_activate_first_inactive(pwq))
- ;
+ /*
+ * Round-robin through pwq's activating the first inactive work item
+ * until max_active is filled.
+ */
+ do {
+ struct pool_workqueue *pwq;

- kick_pool(pwq->pool);
+ activated = false;
+ for_each_pwq(pwq, wq) {
+ unsigned long flags;

- raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
- }
+ /* can be called during early boot w/ irq disabled */
+ raw_spin_lock_irqsave(&pwq->pool->lock, flags);
+ if (pwq_activate_first_inactive(pwq)) {
+ activated = true;
+ kick_pool(pwq->pool);
+ }
+ raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
+ }
+ } while (activated);
}

__printf(1, 4)
--
2.43.0