From 8376fe22c7e79c7e90857d39f82aeae6cad6c4b8 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Fri, 3 Aug 2012 10:30:47 -0700
Subject: [PATCH] workqueue: implement mod_delayed_work[_on]()
Workqueue was lacking a mechanism to modify the timeout of an already
pending delayed_work. delayed_work users have been working around
this using several methods - using an explicit timer + work item,
messing directly with delayed_work->timer, and canceling before
re-queueing, all of which are error-prone and/or ugly.
This patch implements mod_delayed_work[_on]() which behaves similarly
to mod_timer() - if the delayed_work is idle, it's queued with the
given delay; otherwise, its timeout is modified to the new value.
Zero @delay guarantees immediate execution.
v2: Updated to reflect try_to_grab_pending() changes. Now safe to be
called from bh context.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
---
include/linux/workqueue.h | 4 +++
kernel/workqueue.c | 53 +++++++++++++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 5f4aeaa9f3e6d..20000305a8a6d 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -390,6 +390,10 @@ extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
extern bool queue_delayed_work(struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
+extern bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
+ struct delayed_work *dwork, unsigned long delay);
+extern bool mod_delayed_work(struct workqueue_struct *wq,
+ struct delayed_work *dwork, unsigned long delay);
extern void flush_workqueue(struct workqueue_struct *wq);
extern void drain_workqueue(struct workqueue_struct *wq);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index b4a4e05c89e11..41ae2c0979fef 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1413,6 +1413,59 @@ bool queue_delayed_work(struct workqueue_struct *wq,
}
EXPORT_SYMBOL_GPL(queue_delayed_work);
+/**
+ * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
+ * @cpu: CPU number to execute work on
+ * @wq: workqueue to use
+ * @dwork: work to queue
+ * @delay: number of jiffies to wait before queueing
+ *
+ * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
+ * modify @dwork's timer so that it expires after @delay. If @delay is
+ * zero, @work is guaranteed to be scheduled immediately regardless of its
+ * current state.
+ *
+ * Returns %false if @dwork was idle and queued, %true if @dwork was
+ * pending and its timer was modified.
+ *
+ * This function is safe to call from any context other than IRQ handler.
+ * See try_to_grab_pending() for details.
+ */
+bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
+ struct delayed_work *dwork, unsigned long delay)
+{
+ unsigned long flags;
+ int ret;
+
+ do {
+ ret = try_to_grab_pending(&dwork->work, true, &flags);
+ } while (unlikely(ret == -EAGAIN));
+
+ if (likely(ret >= 0)) {
+ __queue_delayed_work(cpu, wq, dwork, delay);
+ local_irq_restore(flags);
+ }
+
+ /* -ENOENT from try_to_grab_pending() becomes %true */
+ return ret;
+}
+EXPORT_SYMBOL_GPL(mod_delayed_work_on);
+
+/**
+ * mod_delayed_work - modify delay of or queue a delayed work
+ * @wq: workqueue to use
+ * @dwork: work to queue
+ * @delay: number of jiffies to wait before queueing
+ *
+ * mod_delayed_work_on() on local CPU.
+ */
+bool mod_delayed_work(struct workqueue_struct *wq, struct delayed_work *dwork,
+ unsigned long delay)
+{
+ return mod_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
+}
+EXPORT_SYMBOL_GPL(mod_delayed_work);
+
/**
* worker_enter_idle - enter idle state
* @worker: worker which is entering idle state
--
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