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Date: Mon, 03 Mar 2008 12:22:38 +0100
From: Philippe Gerum <philippe.gerum@domain.hid>
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Subject: Re: [Xenomai-help] rt_cond_wait doesn't timeout (xenomai 2.4.1)
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To: Anders Blomdell <anders.blomdell@domain.hid>
Cc: xenomai-help <xenomai@xenomai.org>

Anders Blomdell wrote:
> Philippe Gerum wrote:
>> Anders Blomdell wrote:
>>> Gilles Chanteperdrix wrote:
>>>> On Fri, Feb 29, 2008 at 5:54 PM, Anders Blomdell
>>>> <anders.blomdell@domain.hid> wrote:
>>>>> Hi,
>>>>>
>>>>>  with xenomai 2.4.1 my call to:
>>>>>
>>>>>   rt_cond_wait(&cond, &mutex, 1000);
>>>>>
>>>>>  doesn't timeout (signalling works OK). Kernel version is 2.6.23.12, can it be
>>>>>  due to CONFIG_NO_HZ=y, or have I misunderstood something?
>>>> What is your system timer setting ? Are you running in periodic or
>>>> aperiodic mode ? If aperiodic, 1000 ticks means 1000 ns, that is 1us,
>>>> so rt_cond_wait should return instantaneously.
>>> OK, here comes a simplified program that just outputs A, and then hangs.
>>>
>> I can't reproduce this issue with your test code here, but this might be
>> the sign of some timer race depending on how fast is the hw.
>>
>> By hanging, I assume the box is still ok, right?
>> If so, could you please send the output of /proc/xenomai/stat,
>> /proc/xenomai/sched, /proc/xenomai/timer and /proc/xenomai/timerstat/master?
>>
>> TIA,
>>
>> cat /proc/xenomai/stat
> CPU  PID    MSW        CSW        PF    STAT       %CPU  NAME
>   0  0      0          108606586  0     00500080  100.0  ROOT/0
>   0  0      0          54113426   0     00000082    0.0  rtnet-stack
>   0  0      0          1          0     00000082    0.0  rtnet-rtpc
>   0  22291  2          3          0     00300186    0.0  main
>   0  0      0          107816863  0     00000000    0.0  IRQ22: rt_eepro100
>   0  0      0          617309219  0     00000000    0.0  IRQ233: [timer]
> 
>> cat /proc/xenomai/sched
> CPU  PID    PRI      PERIOD     TIMEOUT    TIMEBASE  STAT       NAME
>   0  0       -1      0          0          master    R          ROOT/0
>   0  0       98      0          0          master    W          rtnet-stack
>   0  0        0      0          0          master    W          rtnet-rtpc
>   0  22291    1      0          0          master    w          main
> 
>> cat /proc/xenomai/timer
> status=on+watchdog:setup=0:clock=8061167744254256:timerdev=lapic:clockdev=tsc
> 
>> cat /proc/xenomai/timerstat/master
> CPU  SCHEDULED   FIRED       TIMEOUT    INTERVAL   HANDLER      NAME
> 0    1049107334  506070537   324149     -          NULL         [host-timer/0]
> 0    3358790     3358789     662553305  1000000000  xnpod_watch  [watchdog]
> 0    1           1           -          -          xnthread_ti  main
> 
> 

Thanks. It looks like the timer did tick but the wakeup event was
missed. The thread is still waiting for it (stat xxxxxxx6 means
delayed+pending, which is the mode rt_cond_wait() sets for the thread).
We do have a problem, it seems.

-- 
Philippe.