Messages in this thread | | | Date | Tue, 23 Nov 2004 12:46:39 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm2-V0.7.30-2 |
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* Ingo Molnar <mingo@elte.hu> wrote:
> * Mark_H_Johnson@raytheon.com <Mark_H_Johnson@raytheon.com> wrote: > > > - echo 0 > /proc/sys/kernel/preempt_wakeup_timing [entered, but > > display was frozen at this point and did not see newline nor any > > further output] > > managed to reproduce this on an SMP box but not on an UP box, so i > think this is SMP related. It definitely happens almost immediately > after preempt_wakeup_timing is reset - or after preempt_max_timing is > reset. (Perhaps a dump_stack() from the wrong place, or something > like that.)
The lockup was caused by the mutex wakeup being done under the PI lock, and if a new critical-section latency is reported within try_to_wake_up then the trylock done there deadlocked. The NMI watchdog triggered but the printks done there deadlocked as well.
I fixed both the deadlock scenario, and made the NMI printout path more robust to get the messages out to the console in even such a case.
The fixes are in the latest (-30-4) patch which can be found at the usual place:
http://redhat.com/~mingo/realtime-preempt/
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