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workqueue: Reap workers via kthread_stop() and remove detach_completion

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The code to kick off the destruction of workers is now in a process
context (idle_cull_fn()), so kthread_stop() can be used in the process
context to replace the work of pool->detach_completion.

The wakeup in wake_dying_workers() is unneeded after this change, but it
is harmless, jut keep it here until next patch renames wake_dying_workers()
rather than renaming it again and again.

Cc: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Lai Jiangshan 2024-06-21 15:32:22 +08:00 committed by Tejun Heo
parent b56c720718
commit 68f83057b9
1 changed files with 19 additions and 16 deletions
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35
kernel/workqueue.c
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@ -216,7 +216,6 @@ struct worker_pool {
struct worker *manager; /* L: purely informational */
struct list_head workers; /* A: attached workers */
struct list_head dying_workers; /* A: workers about to die */
struct completion *detach_completion; /* all workers detached */
struct ida worker_ida; /* worker IDs for task name */
@ -2696,7 +2695,6 @@ static void worker_attach_to_pool(struct worker *worker,
static void worker_detach_from_pool(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
struct completion *detach_completion = NULL;
/* there is one permanent BH worker per CPU which should never detach */
WARN_ON_ONCE(pool->flags & POOL_BH);
@ -2707,15 +2705,10 @@ static void worker_detach_from_pool(struct worker *worker)
list_del(&worker->node);
worker->pool = NULL;
if (list_empty(&pool->workers) && list_empty(&pool->dying_workers))
detach_completion = pool->detach_completion;
mutex_unlock(&wq_pool_attach_mutex);
/* clear leftover flags without pool->lock after it is detached */
worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
if (detach_completion)
complete(detach_completion);
}
/**
@ -2816,10 +2809,9 @@ static void unbind_worker(struct worker *worker)
static void wake_dying_workers(struct list_head *cull_list)
{
struct worker *worker, *tmp;
struct worker *worker;
list_for_each_entry_safe(worker, tmp, cull_list, entry) {
list_del_init(&worker->entry);
list_for_each_entry(worker, cull_list, entry) {
unbind_worker(worker);
/*
* If the worker was somehow already running, then it had to be
@ -2835,6 +2827,17 @@ static void wake_dying_workers(struct list_head *cull_list)
}
}
static void reap_dying_workers(struct list_head *cull_list)
{
struct worker *worker, *tmp;
list_for_each_entry_safe(worker, tmp, cull_list, entry) {
list_del_init(&worker->entry);
kthread_stop_put(worker->task);
kfree(worker);
}
}
/**
* set_worker_dying - Tag a worker for destruction
* @worker: worker to be destroyed
@ -2866,6 +2869,9 @@ static void set_worker_dying(struct worker *worker, struct list_head *list)
list_move(&worker->entry, list);
list_move(&worker->node, &pool->dying_workers);
/* get an extra task struct reference for later kthread_stop_put() */
get_task_struct(worker->task);
}
/**
@ -2949,6 +2955,8 @@ static void idle_cull_fn(struct work_struct *work)
raw_spin_unlock_irq(&pool->lock);
wake_dying_workers(&cull_list);
mutex_unlock(&wq_pool_attach_mutex);
reap_dying_workers(&cull_list);
}
static void send_mayday(struct work_struct *work)
@ -3330,7 +3338,6 @@ woke_up:
ida_free(&pool->worker_ida, worker->id);
worker_detach_from_pool(worker);
WARN_ON_ONCE(!list_empty(&worker->entry));
kfree(worker);
return 0;
}
@ -4863,7 +4870,6 @@ static void rcu_free_pool(struct rcu_head *rcu)
*/
static void put_unbound_pool(struct worker_pool *pool)
{
DECLARE_COMPLETION_ONSTACK(detach_completion);
struct worker *worker;
LIST_HEAD(cull_list);
@ -4917,12 +4923,9 @@ static void put_unbound_pool(struct worker_pool *pool)
wake_dying_workers(&cull_list);
if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers))
pool->detach_completion = &detach_completion;
mutex_unlock(&wq_pool_attach_mutex);
if (pool->detach_completion)
wait_for_completion(pool->detach_completion);
reap_dying_workers(&cull_list);
/* shut down the timers */
del_timer_sync(&pool->idle_timer);