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workqueue: Add warnings and ensure one among WQ_PERCPU or WQ_UNBOUND is present

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Currently there are no checks in order to enforce the use of one between
WQ_PERCPU or WQ_UNBOUND.

So act as following:
- if neither of them is present, set WQ_PERCPU
- if both are present, remove WQ_PERCPU

Along with this change, WARN_ONCE(), so that the code still uses both or
neither of them, can be changed.

Link: https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Marco Crivellari
2026-05-29 15:06:40 +02:00
committed by Tejun Heo
parent 64d8eae3f8
commit 21c05ca88a
1 changed files with 18 additions and 1 deletions
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kernel/workqueue.c
+18 -1
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@@ -5802,7 +5802,7 @@ static struct workqueue_struct *__alloc_workqueue(const char *fmt,
/* see the comment above the definition of WQ_POWER_EFFICIENT */
if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
flags |= WQ_UNBOUND;
flags = (flags & ~WQ_PERCPU) | WQ_UNBOUND;
/* allocate wq and format name */
if (flags & WQ_UNBOUND)
@@ -5826,6 +5826,23 @@ static struct workqueue_struct *__alloc_workqueue(const char *fmt,
pr_warn_once("workqueue: name exceeds WQ_NAME_LEN. Truncating to: %s\n",
wq->name);
/*
* One among WQ_PERCPU and WQ_UNBOUND must be set, but not both.
* - If neither is set, default to WQ_PERCPU
* - If both are set, default to WQ_UNBOUND
*
* This code can be removed after workqueue are unbound by default
*/
if (unlikely(!(flags & (WQ_UNBOUND | WQ_PERCPU)))) {
WARN_ONCE(1, "workqueue: %s is using neither WQ_PERCPU or WQ_UNBOUND. "
"Setting WQ_PERCPU.\n", wq->name);
flags |= WQ_PERCPU;
} else if (unlikely((flags & WQ_PERCPU) && (flags & WQ_UNBOUND))) {
WARN_ONCE(1, "workqueue: %s uses both WQ_PERCPU and WQ_UNBOUND. "
"Dropped WQ_PERCPU, keeping WQ_UNBOUND.\n", wq->name);
flags &= ~WQ_PERCPU;
}
if (flags & WQ_BH) {
/*
* BH workqueues always share a single execution context per CPU