FAILED: patch "[PATCH] kthread_worker: split code for canceling the delayed work" failed to apply to 4.14-stable tree

PATCH [email protected] 1 participant 1 message Jun 27, 2021 Stable branch

Share & tools

[email protected]

author maintainer

2021-06-27 14:24 UTC #0 lore raw

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 34b3d5344719d14fd2185b2d9459b3abcb8cf9d8 Mon Sep 17 00:00:00 2001
From: Petr Mladek <[email protected]>
Date: Thu, 24 Jun 2021 18:39:45 -0700
Subject: [PATCH] kthread_worker: split code for canceling the delayed work
timer

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/[email protected] open here

Signed-off-by Petr Mladek <[email protected]>

Cc <[email protected]>

Cc Martin Liu <[email protected]>

Cc Minchan Kim <[email protected]>

Cc Nathan Chancellor <[email protected]>

Cc Nick Desaulniers <[email protected]>

Cc Oleg Nesterov <[email protected]>

Cc Tejun Heo <[email protected]>

Cc <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Signed-off-by Linus Torvalds <[email protected]>

kernel/kthread.c +29 ~~-17~~

index fe3f2a40d61e..121a0e1fc659 100644
@@ -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