Messages in this thread Patch in this message | | | Date | Fri, 29 Oct 2004 23:25:45 +0200 | From | Ingo Molnar <> | Subject | Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4] |
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* Florian Schmidt <mista.tapas@gmx.net> wrote:
> > do you compile jackd from sources? If yes then could you try the patch > > below? With this added, the kernel will produce a stackdump whenever > > jackd does an 'illegal' sleep. > > > > Also, could you do a small modification to kernel/sched.c and remove > > this line: > > > > send_sig(SIGUSR1, current, 1); > > > > just to make it easier to get Jack up and running. (by default an > > atomicity violation triggers a signal to make it easier to debug it in > > userspace, but i suspect there will be alot of such violations so jackd > > would stop all the time.) > > [snip] > > will do so. btw: i think i'm a bit confused right now. What debugging > features should i have enabled for this test?
this particular one (atomicity-checking) is always-enabled if you have the -RT patch applied (it's a really cheap check).
for the 'application-triggered tracing' facility we talked about earlier is only active if LATENCY_TRACING is enabled. In that case to turn the tracer on, call:
gettimeofday(0,1);
and to turn the tracer off and save the current trace into /proc/latency_trace, call:
gettimeofday(0,0);
or apply the patch below - i've added the tracer bits too. I've added a simple limit: all delays above 2 msec will be saved - you might want to do a maximum search there or something. And dont forget to:
echo 2 > /proc/sys/kernel/trace_enabled
to activate the jackd-triggered kernel tracer.
Ingo
--- jack-audio-connection-kit-0.99.0/drivers/alsa/alsa_driver.c.orig +++ jack-audio-connection-kit-0.99.0/drivers/alsa/alsa_driver.c @@ -1161,6 +1161,7 @@ alsa_driver_wait (alsa_driver_t *driver, unsigned int p_timed_out, c_timed_out; unsigned int ci = 0; unsigned int nfds; + int ret; nfds = 0; @@ -1194,7 +1195,20 @@ alsa_driver_wait (alsa_driver_t *driver, poll_enter = jack_get_microseconds (); - if (poll (driver->pfd, nfds, driver->poll_timeout) < 0) { + gettimeofday((void *)1,(void *)0); // atomic off + + gettimeofday((void *)0,(void *)1); // start tracing + + ret = poll (driver->pfd, nfds, driver->poll_timeout); + + poll_ret = jack_get_microseconds (); + + if (poll_ret - poll_enter > 2000) + gettimeofday((void *)0,(void *)0); // save trace + + gettimeofday((void *)1,(void *)1); // atomic on + + if (ret < 0) { if (errno == EINTR) { printf ("poll interrupt\n"); @@ -1214,8 +1228,6 @@ alsa_driver_wait (alsa_driver_t *driver, } - poll_ret = jack_get_microseconds (); - if (extra_fd < 0) { if (driver->poll_next && poll_ret > driver->poll_next) { *delayed_usecs = poll_ret - driver->poll_next; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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