workqueue: set delayed_work->timer function on initialization

delayed_work->timer.function is currently initialized during
queue_delayed_work_on().  Export delayed_work_timer_fn() and set
delayed_work timer function during delayed_work initialization
together with other fields.

This ensures the timer function is always valid on an initialized
delayed_work.  This is to help mod_delayed_work() implementation.

To detect delayed_work users which diddle with the internal timer,
trigger WARN if timer function doesn't match on queue.

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 30474c4e107c..55392385fe30 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1112,7 +1112,7 @@ bool queue_work(struct workqueue_struct *wq, struct work_struct *work)
 }
 EXPORT_SYMBOL_GPL(queue_work);
 
-static void delayed_work_timer_fn(unsigned long __data)
+void delayed_work_timer_fn(unsigned long __data)
 {
         struct delayed_work *dwork = (struct delayed_work *)__data;
         struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
@@ -1121,6 +1121,7 @@ static void delayed_work_timer_fn(unsigned long __data)
         __queue_work(smp_processor_id(), cwq->wq, &dwork->work);
         local_irq_enable();
 }
+EXPORT_SYMBOL_GPL(delayed_work_timer_fn);
 
 /**
  * queue_delayed_work_on - queue work on specific CPU after delay
@@ -1145,6 +1146,8 @@ bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
                 unsigned int lcpu;
 
+                WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
+                             timer->data != (unsigned long)dwork);
                 BUG_ON(timer_pending(timer));
                 BUG_ON(!list_empty(&work->entry));
 
@@ -1168,8 +1171,6 @@ bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
                 set_work_cwq(work, get_cwq(lcpu, wq), 0);
 
                 timer->expires = jiffies + delay;
-                timer->data = (unsigned long)dwork;
-                timer->function = delayed_work_timer_fn;
 
                 if (unlikely(cpu >= 0))
                         add_timer_on(timer, cpu);