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kthread_worker: split code for canceling the delayed work timer

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Patch series "kthread_worker: Fix race between kthread_mod_delayed_work()
and kthread_cancel_delayed_work_sync()".

This patchset fixes the race between kthread_mod_delayed_work() and
kthread_cancel_delayed_work_sync() including proper return value
handling.

This patch (of 2):

Simple code refactoring as a preparation step for fixing a race between
kthread_mod_delayed_work() and kthread_cancel_delayed_work_sync().

It does not modify the existing behavior.

Link: https://lkml.kernel.org/r/20210610133051.15337-2-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: <jenhaochen@google.com>
Cc: Martin Liu <liumartin@google.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Petr Mladek 2021-06-24 18:39:45 -07:00 committed by Linus Torvalds
parent 7ca3027b72
commit 34b3d53447
1 changed files with 29 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
kernel/kthread.c
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@ -1092,6 +1092,33 @@ void kthread_flush_work(struct kthread_work *work)
}
EXPORT_SYMBOL_GPL(kthread_flush_work);
/*
* Make sure that the timer is neither set nor running and could
* not manipulate the work list_head any longer.
*
* The function is called under worker->lock. The lock is temporary
* released but the timer can't be set again in the meantime.
*/
static void kthread_cancel_delayed_work_timer(struct kthread_work *work,
unsigned long *flags)
{
struct kthread_delayed_work *dwork =
container_of(work, struct kthread_delayed_work, work);
struct kthread_worker *worker = work->worker;
/*
* del_timer_sync() must be called to make sure that the timer
* callback is not running. The lock must be temporary released
* to avoid a deadlock with the callback. In the meantime,
* any queuing is blocked by setting the canceling counter.
*/
work->canceling++;
raw_spin_unlock_irqrestore(&worker->lock, *flags);
del_timer_sync(&dwork->timer);
raw_spin_lock_irqsave(&worker->lock, *flags);
work->canceling--;
}
/*
* This function removes the work from the worker queue. Also it makes sure
* that it won't get queued later via the delayed work's timer.
@ -1106,23 +1133,8 @@ static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
unsigned long *flags)
{
/* Try to cancel the timer if exists. */
if (is_dwork) {
struct kthread_delayed_work *dwork =
container_of(work, struct kthread_delayed_work, work);
struct kthread_worker *worker = work->worker;
/*
* del_timer_sync() must be called to make sure that the timer
* callback is not running. The lock must be temporary released
* to avoid a deadlock with the callback. In the meantime,
* any queuing is blocked by setting the canceling counter.
*/
work->canceling++;
raw_spin_unlock_irqrestore(&worker->lock, *flags);
del_timer_sync(&dwork->timer);
raw_spin_lock_irqsave(&worker->lock, *flags);
work->canceling--;
}
if (is_dwork)
kthread_cancel_delayed_work_timer(work, flags);
/*
* Try to remove the work from a worker list. It might either