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Message-ID: <CAJNi4rOgYmmtOaXVqYB9sAxDmRhGhS_vVXmZbCbMjvFCQsdjCw@mail.gmail.com>
Date: Mon, 5 Dec 2022 14:18:35 +0800
From: richard clark <richard.xnu.clark@...il.com>
To: Lai Jiangshan <jiangshanlai@...il.com>
Cc: tj@...nel.org, linux-kernel@...r.kernel.org
Subject: work item still be scheduled to execute after destroy_workqueue?
Hi Lai and Tejun,
Why can the work still be queued to and executed when queueing it to a
wq has been destroyed, for instance, the below code snippet in a
kernel module:
---------------------->8---------------------
struct workqueue_struct *wq0;
#define MAX_ACTIVE_WORKS (3)
static void work0_func(struct work_struct *work);
static void work1_func(struct work_struct *work);
static void work2_func(struct work_struct *work);
static DECLARE_WORK(w0, work0_func);
static DECLARE_WORK(w1, work1_func);
static DECLARE_WORK(w2, work2_func);
/* work->func */
static void work0_func(struct work_struct *work)
{
pr_info("+%s begins to sleep\n", __func__);
/* sleep for 10s */
schedule_timeout_interruptible(msecs_to_jiffies(10000));
pr_info("+%s after sleep, begin to queue another work\n", __func__);
queue_work_on(1, wq0, &w1);
}
/* work->func */
static void work1_func(struct work_struct *work)
{
pr_info("+%s scheduled\n", __func__);
}
/* work->func */
static void work2_func(struct work_struct *work)
{
pr_info("+%s scheduled\n", __func__);
}
static int destroy_init(void)
{
wq0 = alloc_workqueue("percpu_wq0", 0, MAX_ACTIVE_WORKS);
if (!wq0) {
pr_err("alloc_workqueue failed\n");
return -1;
}
queue_work_on(1, wq0, &w0);
pr_info("Begin to destroy wq0...\n");
destroy_workqueue(wq0);
pr_info("queue w2 to the wq0 after destroyed...\n");
queue_work_on(1, wq0, &w2);
return 0;
}
The output on my x86_64 box is:
[344702.734480] +destroy_init+
[344702.734499] Begin to destroy wq0...
[344702.734516] +work0_func begins to sleep
[344712.791607] +work0_func after sleep, begin to queue another work
[344712.791620] +work1_func scheduled
[344712.791649] queue w2 to the wq0 after destroyed...
[344712.791663] +work2_func scheduled <------------- work 2 still be scheduled?
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