From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Petr Mladek <pmladek@suse.com>,
jenhaochen@google.com, Martin Liu <liumartin@google.com>,
Minchan Kim <minchan@google.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Oleg Nesterov <oleg@redhat.com>, Tejun Heo <tj@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 4.9 7/9] kthread_worker: split code for canceling the delayed work timer
Date: Fri, 9 Jul 2021 15:18:34 +0200 [thread overview]
Message-ID: <20210709131552.455038494@linuxfoundation.org> (raw)
In-Reply-To: <20210709131542.410636747@linuxfoundation.org>
From: Petr Mladek <pmladek@suse.com>
commit 34b3d5344719d14fd2185b2d9459b3abcb8cf9d8 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/kthread.c | 46 +++++++++++++++++++++++++++++-----------------
1 file changed, 29 insertions(+), 17 deletions(-)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -952,6 +952,33 @@ void kthread_flush_work(struct kthread_w
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++;
+ spin_unlock_irqrestore(&worker->lock, *flags);
+ del_timer_sync(&dwork->timer);
+ 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.
*
@@ -965,23 +992,8 @@ static bool __kthread_cancel_work(struct
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++;
- spin_unlock_irqrestore(&worker->lock, *flags);
- del_timer_sync(&dwork->timer);
- 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
next prev parent reply other threads:[~2021-07-09 13:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-09 13:18 [PATCH 4.9 0/9] 4.9.275-rc1 review Greg Kroah-Hartman
2021-07-09 13:18 ` [PATCH 4.9 1/9] include/linux/mmdebug.h: make VM_WARN* non-rvals Greg Kroah-Hartman
2021-07-09 13:18 ` [PATCH 4.9 2/9] mm: add VM_WARN_ON_ONCE_PAGE() macro Greg Kroah-Hartman
2021-07-09 13:18 ` [PATCH 4.9 3/9] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Greg Kroah-Hartman
2021-07-09 13:18 ` [PATCH 4.9 4/9] mm, futex: fix shared futex pgoff on shmem huge page Greg Kroah-Hartman
2021-07-09 13:18 ` [PATCH 4.9 5/9] scsi: sr: Return appropriate error code when disk is ejected Greg Kroah-Hartman
2021-07-09 13:18 ` [PATCH 4.9 6/9] drm/nouveau: fix dma_address check for CPU/GPU sync Greg Kroah-Hartman
2021-07-09 13:18 ` Greg Kroah-Hartman [this message]
2021-07-09 13:18 ` [PATCH 4.9 8/9] kthread: prevent deadlock when kthread_mod_delayed_work() races with kthread_cancel_delayed_work_sync() Greg Kroah-Hartman
2021-07-09 13:18 ` [PATCH 4.9 9/9] xen/events: reset active flag for lateeoi events later Greg Kroah-Hartman
2021-07-09 21:43 ` [PATCH 4.9 0/9] 4.9.275-rc1 review Shuah Khan
2021-07-10 14:12 ` Naresh Kamboju
2021-07-10 19:50 ` Guenter Roeck
2021-07-11 3:58 ` Florian Fainelli
2021-07-12 16:46 ` Florian Fainelli
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