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authorPetr Mladek <pmladek@suse.com>2016-10-11 23:55:46 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-12 01:06:33 +0300
commit9a6b06c8d9a220860468aadb2f1c726570813bf9 (patch)
tree4bed10bb36fdb1f0b0cbfd97a00a85a4f02db80b /kernel
parent37be45d49dec2a411e29d50c9597cfe8184b5645 (diff)
downloadlinux-9a6b06c8d9a220860468aadb2f1c726570813bf9.tar.xz
kthread: allow to modify delayed kthread work
There are situations when we need to modify the delay of a delayed kthread work. For example, when the work depends on an event and the initial delay means a timeout. Then we want to queue the work immediately when the event happens. This patch implements kthread_mod_delayed_work() as inspired workqueues. It cancels the timer, removes the work from any worker list and queues it again with the given timeout. A very special case is when the work is being canceled at the same time. It might happen because of the regular kthread_cancel_delayed_work_sync() or by another kthread_mod_delayed_work(). In this case, we do nothing and let the other operation win. This should not normally happen as the caller is supposed to synchronize these operations a reasonable way. Link: http://lkml.kernel.org/r/1470754545-17632-11-git-send-email-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Borislav Petkov <bp@suse.de> Cc: Michal Hocko <mhocko@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kthread.c53
1 files changed, 53 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 20505c632bc3..c1fcc63fa605 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -976,6 +976,59 @@ static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
return false;
}
+/**
+ * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
+ * @worker: kthread worker to use
+ * @dwork: kthread delayed work to queue
+ * @delay: number of jiffies to wait before queuing
+ *
+ * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
+ * modify @dwork's timer so that it expires after @delay. If @delay is zero,
+ * @work is guaranteed to be queued immediately.
+ *
+ * Return: %true if @dwork was pending and its timer was modified,
+ * %false otherwise.
+ *
+ * A special case is when the work is being canceled in parallel.
+ * It might be caused either by the real kthread_cancel_delayed_work_sync()
+ * or yet another kthread_mod_delayed_work() call. We let the other command
+ * win and return %false here. The caller is supposed to synchronize these
+ * operations a reasonable way.
+ *
+ * This function is safe to call from any context including IRQ handler.
+ * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
+ * for details.
+ */
+bool kthread_mod_delayed_work(struct kthread_worker *worker,
+ struct kthread_delayed_work *dwork,
+ unsigned long delay)
+{
+ struct kthread_work *work = &dwork->work;
+ unsigned long flags;
+ int ret = false;
+
+ spin_lock_irqsave(&worker->lock, flags);
+
+ /* Do not bother with canceling when never queued. */
+ if (!work->worker)
+ goto fast_queue;
+
+ /* Work must not be used with >1 worker, see kthread_queue_work() */
+ WARN_ON_ONCE(work->worker != worker);
+
+ /* Do not fight with another command that is canceling this work. */
+ if (work->canceling)
+ goto out;
+
+ ret = __kthread_cancel_work(work, true, &flags);
+fast_queue:
+ __kthread_queue_delayed_work(worker, dwork, delay);
+out:
+ spin_unlock_irqrestore(&worker->lock, flags);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
+
static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
{
struct kthread_worker *worker = work->worker;