Re: RT and Cascade interrupts

[Trond Myklebust <trond.myklebust@fys.uio.no>]

on den 01.06.2005 Klokka 18:51 (-0400) skreiv Trond Myklebust:
> Could you then apply the following debugging patch? It should warn you
> in case something happens to corrupt base->running_timer (something
> which would screw up del_timer_sync()). I'm not sure that can happen,
> but it might be worth checking.

Oops. You don't want to return without releasing the spinlock. This
patch should be better...

Cheers,
  Trond

 timer.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletion(-)

Index: linux-2.6.12-rc5-rt-V0.7.47-15/kernel/timer.c
===================================================================
--- linux-2.6.12-rc5-rt-V0.7.47-15.orig/kernel/timer.c
+++ linux-2.6.12-rc5-rt-V0.7.47-15/kernel/timer.c
@@ -436,7 +436,7 @@ static int cascade(tvec_base_t *base, tv
 
 static inline void __run_timers(tvec_base_t *base)
 {
-	struct timer_list *timer;
+	struct timer_list *timer = NULL;
 
 	spin_lock_irq(&base->lock);
 	while (time_after_eq(jiffies, base->timer_jiffies)) {
@@ -444,6 +444,10 @@ static inline void __run_timers(tvec_bas
 		struct list_head *head = &work_list;
  		int index = base->timer_jiffies & TVR_MASK;
 
+		if (unlikely(base->running_timer != timer)) {
+			printk("BUG in line %d: __run_timers() is non-reentrant!\n", __LINE__);
+			goto out;
+		}
 		if (softirq_need_resched()) {
 			/* running_timer might be stale: */
 			set_running_timer(base, NULL);
@@ -459,6 +463,10 @@ static inline void __run_timers(tvec_bas
 			 * valid. Any new jiffy will be taken care of in
 			 * subsequent loops:
 			 */
+			if (unlikely(base->running_timer != timer)) {
+				printk("BUG in line %d: __run_timers() is non-reentrant!\n", __LINE__);
+				goto out;
+			}
 		}
 		/*
 		 * Cascade timers:
@@ -498,7 +506,12 @@ repeat:
 			goto repeat;
 		}
 	}
+	if (unlikely(base->running_timer != timer)) {
+		printk("BUG in line %d: __run_timers() is non-reentrant!\n", __LINE__);
+		goto out;
+	}
 	set_running_timer(base, NULL);
+out:
 	spin_unlock_irq(&base->lock);
 //	if (waitqueue_active(&base->wait_running_timer))
 		wake_up(&base->wait_for_running_timer);