* Re: possible bug in RP kernel [not found] <20050912105010.701a822f@mango.fruits.de> @ 2005-09-12 9:01 ` Ingo Molnar 2005-09-12 9:14 ` Florian Schmidt 0 siblings, 1 reply; 3+ messages in thread From: Ingo Molnar @ 2005-09-12 9:01 UTC (permalink / raw) To: Florian Schmidt; +Cc: linux-kernel @ vger. kernel. org, Thomas Gleixner * Florian Schmidt <mista.tapas@gmx.net> wrote: > Problem is: i wrote a small test program running at prio 80 that > simply busy loops for about 15 seconds. It seems from the log output > that the main thread never wakes up during the time of the test > program running. > > Sep 12 10:36:07 mango rt_watchdog: count 5 > Sep 12 10:36:30 mango rt_watchdog: count 6 > ^^ > 23 seconds gap between two wakeups > > Maybe my understanding of how sched fifo works is wrong, but i assumed > a higher prio thread shold get woken up from a sleep by the scheduler > which gets run by the timer interrupt [which is still non > preemptible]. depending on what type of timeout you are using you'll also need to chrt the softirq-timer kernel thread(s) to prio 99. Otherwise the timer fn will have no chance to be executed. There's work going on by Thomas to make such things automatic, by prioritizing timers. If you have HRT enabled in the .config then it should mostly be automatic already though. Ingo ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: possible bug in RP kernel 2005-09-12 9:01 ` possible bug in RP kernel Ingo Molnar @ 2005-09-12 9:14 ` Florian Schmidt 2005-09-12 9:31 ` Ingo Molnar 0 siblings, 1 reply; 3+ messages in thread From: Florian Schmidt @ 2005-09-12 9:14 UTC (permalink / raw) To: Ingo Molnar; +Cc: linux-kernel @ vger. kernel. org, Thomas Gleixner On Mon, 12 Sep 2005 11:01:15 +0200 Ingo Molnar <mingo@elte.hu> wrote: > > 23 seconds gap between two wakeups > > > > Maybe my understanding of how sched fifo works is wrong, but i assumed > > a higher prio thread shold get woken up from a sleep by the scheduler > > which gets run by the timer interrupt [which is still non > > preemptible]. > > depending on what type of timeout you are using you'll also need to chrt > the softirq-timer kernel thread(s) to prio 99. Otherwise the timer fn > will have no chance to be executed. There's work going on by Thomas to > make such things automatic, by prioritizing timers. If you have HRT > enabled in the .config then it should mostly be automatic already > though. Ah, thanks for the info. So it is a user (me) bug in the end :) This has helped. Actually the code i had attached had another bug in it. But that wasn't the responsible one. Thanks again, and sorry for the multiple mails, Florian Schmidt -- Palimm Palimm! http://tapas.affenbande.org ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: possible bug in RP kernel 2005-09-12 9:14 ` Florian Schmidt @ 2005-09-12 9:31 ` Ingo Molnar 0 siblings, 0 replies; 3+ messages in thread From: Ingo Molnar @ 2005-09-12 9:31 UTC (permalink / raw) To: Florian Schmidt; +Cc: linux-kernel @ vger. kernel. org, Thomas Gleixner * Florian Schmidt <mista.tapas@gmx.net> wrote: > On Mon, 12 Sep 2005 11:01:15 +0200 > Ingo Molnar <mingo@elte.hu> wrote: > > > > 23 seconds gap between two wakeups > > > > > > Maybe my understanding of how sched fifo works is wrong, but i assumed > > > a higher prio thread shold get woken up from a sleep by the scheduler > > > which gets run by the timer interrupt [which is still non > > > preemptible]. > > > > depending on what type of timeout you are using you'll also need to chrt > > the softirq-timer kernel thread(s) to prio 99. Otherwise the timer fn > > will have no chance to be executed. There's work going on by Thomas to > > make such things automatic, by prioritizing timers. If you have HRT > > enabled in the .config then it should mostly be automatic already > > though. > > Ah, > > thanks for the info. So it is a user (me) bug in the end :) This has > helped. Actually the code i had attached had another bug in it. But > that wasn't the responsible one. well, it's not really your 'bug' - the priority setup isnt very intuitive at the moment, and the goal is to automate as much of it as possible. The way various system threads interact is highly implementation dependent, and you shouldnt really be required to know about softirq-timer. We'll try to simplify these things as much as possible. Ingo ^ permalink raw reply [flat|nested] 3+ messages in thread
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2005-09-12 9:01 ` possible bug in RP kernel Ingo Molnar
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2005-09-12 9:31 ` Ingo Molnar
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