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author | Petr Mladek <pmladek@suse.com> | 2021-06-24 18:39:45 -0700 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-07-11 12:48:12 +0200 |
commit | 5f7c8a41b8a96709c165f41cc793c8a0a6eee160 (patch) | |
tree | 918ac7fdf83a29d2b6e0727a142a5a422cb52afb | |
parent | d63af6c931f73b4597e37816ed4e77ee690ada82 (diff) | |
download | linux-stable-5f7c8a41b8a96709c165f41cc793c8a0a6eee160.tar.gz linux-stable-5f7c8a41b8a96709c165f41cc793c8a0a6eee160.tar.bz2 linux-stable-5f7c8a41b8a96709c165f41cc793c8a0a6eee160.zip |
kthread_worker: split code for canceling the delayed work timer
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>
-rw-r--r-- | kernel/kthread.c | 46 |
1 files changed, 29 insertions, 17 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c index fd6f9322312a..478400ed9fe9 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -979,6 +979,33 @@ 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++; + 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. * @@ -992,23 +1019,8 @@ 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++; - 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 |