Messages in this thread Patch in this message |  | | | Subject | Re: [ANNOUNCE] 2.6.15-rc5-hrt2 - hrtimers based high resolution patches | | From | Steven Rostedt <> | | Date | Tue, 13 Dec 2005 16:05:27 -0500 |
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Thomas and Ingo,
I found a bug in 2.6.15-rc5-rt1 that was due to a race in the hrtimers code. This bug is most likely in the vanilla hrtimers code as well.
I added a HRTIMER_RUNNING state because there's a moment in the run_hrtimer_queues that turns interrupts on and releases the base lock. In this time, a remove_hrtimer can be called while the state is still HRTIMER_PENDING_CALLBACK, but it has been removed off the list. The remove_hrtimer will then try to remove this again.
Since I couldn't think of which state to use, I created the HRTIMER_RUNNING, and used that instead.
I have a program (a simple jitter test) that, with out the patch, reliably crashes the 2.6.15-rc5-rt1 on a slow UP machine. With the patch, it runs solidly, so I know this is the reason for the crash.
-- Steve
Index: linux-2.6.15-rc5-rt1/kernel/hrtimer.c =================================================================== --- linux-2.6.15-rc5-rt1.orig/kernel/hrtimer.c 2005-12-13 15:51:52.000000000 -0500 +++ linux-2.6.15-rc5-rt1/kernel/hrtimer.c 2005-12-13 15:53:36.000000000 -0500 @@ -846,6 +846,7 @@ data = timer->data; set_curr_timer(base, timer); list_del(&timer->list); + timer->state = HRTIMER_RUNNING; spin_unlock_irq(&base->lock); /* @@ -904,6 +905,7 @@ data = timer->data; set_curr_timer(base, timer); __remove_hrtimer(timer, base); + timer->state = HRTIMER_RUNNING; spin_unlock_irq(&base->lock); /* Index: linux-2.6.15-rc5-rt1/include/linux/hrtimer.h =================================================================== --- linux-2.6.15-rc5-rt1.orig/include/linux/hrtimer.h 2005-12-13 15:51:40.000000000 -0500 +++ linux-2.6.15-rc5-rt1/include/linux/hrtimer.h 2005-12-13 15:55:21.000000000 -0500 @@ -41,6 +41,7 @@ enum hrtimer_state { HRTIMER_INACTIVE, /* Timer is inactive */ HRTIMER_EXPIRED, /* Timer is expired */ + HRTIMER_RUNNING, /* Timer is currently running */ HRTIMER_PENDING, /* Timer is pending */ HRTIMER_PENDING_CALLBACK, /* Timer is expired, callback pending */ };
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