Re: SCHED_FIFO: sleep times longer than expected (AGAIN)
Harald Kirsch (kir@iitb.fhg.de)
Fri, 23 Aug 1996 12:04:39 +0200
>> rti834 overflow, status=0x14a8, last sleep=0.075978
>> stamp[63] = 0.001496 at 840787263.009563 by timer
>> stamp[62] = 0.000074 at 840787263.008067 by read
>> stamp[61] = 0.008468 at 840787263.007993 by wait/end
>> stamp[60] = 0.010016 at 840787262.999525 by timer
>> stamp[59] = 0.009966 at 840787262.989509 by timer
>> stamp[58] = 0.010019 at 840787262.979543 by timer
>> stamp[57] = 0.010085 at 840787262.969524 by timer
>> stamp[56] = 0.010007 at 840787262.959439 by timer
>> stamp[55] = 0.009890 at 840787262.949432 by timer
>> stamp[54] = 0.007545 at 840787262.939542 by timer
>> stamp[53] = 0.000995 at 840787262.931997 by wait/start
>> stamp[52] = 0.000074 at 840787262.931002 by read
>> stamp[51] = 0.000474 at 840787262.930928 by wait/end
>> stamp[50] = 0.008822 at 840787262.930454 by timer
>> stamp[49] = 0.000863 at 840787262.921632 by wait/start
>
>if i read your log right, then your program is blocking on a read()
>operation. Thats pretty much normal ... there is no "looping", your
>program is waiting for the read request to finish.
>
>run a program that does something like this:
>
> for(;;);
>
>and if >this< program gets interrupted for 100 msecs, then we have a
>problem :)
>
>-- mingo
The stamps are written by my driver and 'wait/start' is the stamp
immediately before interuptible_sleep_on, while 'wait/end' is in the
source line after interuptible_sleep_on. Whenever the log says 'timer',
wake_up is called, i.e. we should see a 'wait/end' immediately
afterwards (because the process is SCHED_FIFO), like at stamp[50],
stamp[51]. There would probably be no 'read' stamp, because no data is
yet available from the hardware, but certainly 'wait/end' should show up
immediatly after a 'timer' stamp.
Harald.
-------------------------------------------------+------------------
Harald Kirsch, kir@iitb.fhg.de, +49 721 6091 384 | This message is
FhG/IITB, Fraunhoferstr.1, 76131 Karlsruhe | subject oriented.