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Subject[PATCH 1/2] kthread: convert worker lock to raw spinlock
Date
From: Julia Cartwright <julia@ni.com>

In order to enable the queuing of kthread work items from hardirq
context even when PREEMPT_RT_FULL is enabled, convert the worker
spin_lock to a raw_spin_lock.

This is only acceptable to do because the work performed under the lock
is well-bounded and minimal.

Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Reported-and-tested-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Reported-by: Tim Sander <tim@krieglstein.org>
Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/kthread.h | 4 ++--
kernel/kthread.c | 42 ++++++++++++++++++++---------------------
2 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index c1961761311db..6b8c064f0cbcd 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -85,7 +85,7 @@ enum {

struct kthread_worker {
unsigned int flags;
- spinlock_t lock;
+ raw_spinlock_t lock;
struct list_head work_list;
struct list_head delayed_work_list;
struct task_struct *task;
@@ -106,7 +106,7 @@ struct kthread_delayed_work {
};

#define KTHREAD_WORKER_INIT(worker) { \
- .lock = __SPIN_LOCK_UNLOCKED((worker).lock), \
+ .lock = __RAW_SPIN_LOCK_UNLOCKED((worker).lock), \
.work_list = LIST_HEAD_INIT((worker).work_list), \
.delayed_work_list = LIST_HEAD_INIT((worker).delayed_work_list),\
}
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 087d18d771b53..5641b55783a6f 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -599,7 +599,7 @@ void __kthread_init_worker(struct kthread_worker *worker,
struct lock_class_key *key)
{
memset(worker, 0, sizeof(struct kthread_worker));
- spin_lock_init(&worker->lock);
+ raw_spin_lock_init(&worker->lock);
lockdep_set_class_and_name(&worker->lock, key, name);
INIT_LIST_HEAD(&worker->work_list);
INIT_LIST_HEAD(&worker->delayed_work_list);
@@ -641,21 +641,21 @@ int kthread_worker_fn(void *worker_ptr)

if (kthread_should_stop()) {
__set_current_state(TASK_RUNNING);
- spin_lock_irq(&worker->lock);
+ raw_spin_lock_irq(&worker->lock);
worker->task = NULL;
- spin_unlock_irq(&worker->lock);
+ raw_spin_unlock_irq(&worker->lock);
return 0;
}

work = NULL;
- spin_lock_irq(&worker->lock);
+ raw_spin_lock_irq(&worker->lock);
if (!list_empty(&worker->work_list)) {
work = list_first_entry(&worker->work_list,
struct kthread_work, node);
list_del_init(&work->node);
}
worker->current_work = work;
- spin_unlock_irq(&worker->lock);
+ raw_spin_unlock_irq(&worker->lock);

if (work) {
__set_current_state(TASK_RUNNING);
@@ -812,12 +812,12 @@ bool kthread_queue_work(struct kthread_worker *worker,
bool ret = false;
unsigned long flags;

- spin_lock_irqsave(&worker->lock, flags);
+ raw_spin_lock_irqsave(&worker->lock, flags);
if (!queuing_blocked(worker, work)) {
kthread_insert_work(worker, work, &worker->work_list);
ret = true;
}
- spin_unlock_irqrestore(&worker->lock, flags);
+ raw_spin_unlock_irqrestore(&worker->lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kthread_queue_work);
@@ -843,7 +843,7 @@ void kthread_delayed_work_timer_fn(struct timer_list *t)
if (WARN_ON_ONCE(!worker))
return;

- spin_lock(&worker->lock);
+ raw_spin_lock(&worker->lock);
/* Work must not be used with >1 worker, see kthread_queue_work(). */
WARN_ON_ONCE(work->worker != worker);

@@ -852,7 +852,7 @@ void kthread_delayed_work_timer_fn(struct timer_list *t)
list_del_init(&work->node);
kthread_insert_work(worker, work, &worker->work_list);

- spin_unlock(&worker->lock);
+ raw_spin_unlock(&worker->lock);
}
EXPORT_SYMBOL(kthread_delayed_work_timer_fn);

@@ -908,14 +908,14 @@ bool kthread_queue_delayed_work(struct kthread_worker *worker,
unsigned long flags;
bool ret = false;

- spin_lock_irqsave(&worker->lock, flags);
+ raw_spin_lock_irqsave(&worker->lock, flags);

if (!queuing_blocked(worker, work)) {
__kthread_queue_delayed_work(worker, dwork, delay);
ret = true;
}

- spin_unlock_irqrestore(&worker->lock, flags);
+ raw_spin_unlock_irqrestore(&worker->lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
@@ -951,7 +951,7 @@ void kthread_flush_work(struct kthread_work *work)
if (!worker)
return;

- spin_lock_irq(&worker->lock);
+ raw_spin_lock_irq(&worker->lock);
/* Work must not be used with >1 worker, see kthread_queue_work(). */
WARN_ON_ONCE(work->worker != worker);

@@ -963,7 +963,7 @@ void kthread_flush_work(struct kthread_work *work)
else
noop = true;

- spin_unlock_irq(&worker->lock);
+ raw_spin_unlock_irq(&worker->lock);

if (!noop)
wait_for_completion(&fwork.done);
@@ -996,9 +996,9 @@ static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
* any queuing is blocked by setting the canceling counter.
*/
work->canceling++;
- spin_unlock_irqrestore(&worker->lock, *flags);
+ raw_spin_unlock_irqrestore(&worker->lock, *flags);
del_timer_sync(&dwork->timer);
- spin_lock_irqsave(&worker->lock, *flags);
+ raw_spin_lock_irqsave(&worker->lock, *flags);
work->canceling--;
}

@@ -1045,7 +1045,7 @@ bool kthread_mod_delayed_work(struct kthread_worker *worker,
unsigned long flags;
int ret = false;

- spin_lock_irqsave(&worker->lock, flags);
+ raw_spin_lock_irqsave(&worker->lock, flags);

/* Do not bother with canceling when never queued. */
if (!work->worker)
@@ -1062,7 +1062,7 @@ bool kthread_mod_delayed_work(struct kthread_worker *worker,
fast_queue:
__kthread_queue_delayed_work(worker, dwork, delay);
out:
- spin_unlock_irqrestore(&worker->lock, flags);
+ raw_spin_unlock_irqrestore(&worker->lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
@@ -1076,7 +1076,7 @@ static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
if (!worker)
goto out;

- spin_lock_irqsave(&worker->lock, flags);
+ raw_spin_lock_irqsave(&worker->lock, flags);
/* Work must not be used with >1 worker, see kthread_queue_work(). */
WARN_ON_ONCE(work->worker != worker);

@@ -1090,13 +1090,13 @@ static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
* In the meantime, block any queuing by setting the canceling counter.
*/
work->canceling++;
- spin_unlock_irqrestore(&worker->lock, flags);
+ raw_spin_unlock_irqrestore(&worker->lock, flags);
kthread_flush_work(work);
- spin_lock_irqsave(&worker->lock, flags);
+ raw_spin_lock_irqsave(&worker->lock, flags);
work->canceling--;

out_fast:
- spin_unlock_irqrestore(&worker->lock, flags);
+ raw_spin_unlock_irqrestore(&worker->lock, flags);
out:
return ret;
}
--
2.20.1
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