Messages in this thread Patch in this message | | | Date | Thu, 2 Dec 2004 18:44:21 +0100 | From | Florian Schmidt <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.31-19 |
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On Thu, 2 Dec 2004 14:49:34 +0100 Ingo Molnar <mingo@elte.hu> wrote:
> > * Florian Schmidt <mista.tapas@gmx.net> wrote: > > > Ok, so if i want to find out whether a client violates the RT > > constraints for its process callback i would have to add a call to > > gettimeofday(1,1) at the start of the process callback and > > gettimeofday(1,0) at the end. > > > > Everything which causes a reschedule inbetween will then cause SIGUSR2 > > to be sent to the client for which i could either add a signal handler > > in the client or just use gdb to get notified of it. > > correct. I'd expect there to be a number of less critical reschedules > happening around startup/shutdown of a client, which one could consider > a false positive, but there should be no unexpected rescheduling while > the client is up and running.
Ok,
this simple patch adds the gettimeofday calls around the calling of the process callback:
--- libjack/client.c.orig 2004-12-02 17:55:04.000000000 +0100 +++ libjack/client.c 2004-12-02 17:56:23.000000000 +0100 @@ -1238,6 +1238,9 @@ if (control->sync_cb) jack_call_sync_client (client); + // enable atomicity check for RP kernels + gettimeofday(1,1); + if (control->process) { if (control->process (control->nframes, control->process_arg) @@ -1247,7 +1250,10 @@ } else { control->state = Finished; } - + + // disable atomicity check + gettimeofday(0,1); + if (control->timebase_cb) jack_call_timebase_master (client); The results i see are rather interesting though. Even with a noop jack client (which does nothing but return 0 in the process callback) i get a syslog report everytime i start the client. Client source attached.
Dec 2 18:39:06 mango kernel: jack_test:22743 userspace BUG: scheduling in user-atomic context! Dec 2 18:39:06 mango kernel: [<c02a38b6>] schedule+0x76/0x130 (8) Dec 2 18:39:06 mango kernel: [<c02a44c5>] schedule_timeout+0x85/0xe0 (36) Dec 2 18:39:06 mango kernel: [<c016677f>] do_pollfd+0x4f/0x90 (48) Dec 2 18:39:06 mango kernel: [<c011ceb0>] process_timeout+0x0/0x10 (8) Dec 2 18:39:06 mango kernel: [<c016686a>] do_poll+0xaa/0xd0 (20) Dec 2 18:39:06 mango kernel: [<c01669e2>] sys_poll+0x152/0x230 (48) Dec 2 18:39:06 mango kernel: [<c0165db0>] __pollwait+0x0/0xd0 (36) Dec 2 18:39:06 mango kernel: [<c01025cb>] syscall_call+0x7/0xb (32)
The atomicity check operates on a per task (thread) basis right?
Flo #include <jack/jack.h> #include <iostream> #include <sstream> #include <unistd.h>
jack_client_t *client; jack_port_t *iport; jack_port_t *oport;
int wasted_loops = 0;
int sleep_seconds = 1; int sleep_in_period = 2000; int counter = 0;
int process(jack_nframes_t frames, void *arg) { /* // std::cout << "process callback" << std::endl; jack_default_audio_sample_t *ibuf; ibuf = (jack_default_audio_sample_t*)jack_port_get_buffer(iport, frames);
jack_default_audio_sample_t *obuf; obuf = (jack_default_audio_sample_t*)jack_port_get_buffer(oport, frames);
for (jack_nframes_t frame = 0; frame < frames; frame++) { for (int i = 0; i < wasted_loops; ++i) { // do nothing } obuf[frame] = ibuf[frame]; } counter++; if (counter == sleep_in_period) { //sleep(sleep_seconds); } */ return 0; }
int main(int argc, char *argv[]) { // default = 60 seconds unsigned int seconds_to_run = 60; if (argc > 1) { std::stringstream sec_stream; sec_stream << argv[1]; sec_stream >> seconds_to_run; if (argc > 2) { std::stringstream waste_stream; waste_stream << argv[2]; waste_stream >> wasted_loops; std::cout << "wasted loops: " << wasted_loops << std::endl; } } std::cout << "seconds to run: " << seconds_to_run << std::endl; std::stringstream pid_stream; pid_stream << getpid(); std::cout << "client_new" << std::endl; client = jack_client_new(pid_stream.str().c_str());
std::cout << "port_register." << std::endl; iport = jack_port_register(client, "in", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput|JackPortIsTerminal, 0); oport = jack_port_register(client, "out", JACK_DEFAULT_AUDIO_TYPE, JackPortIsTerminal|JackPortIsOutput, 0);
std::cout << "set_process_callback" << std::endl; jack_set_process_callback(client, process, 0);
std::cout << "activate" << std::endl; jack_activate(client);
std::cout << "running" << std::endl;
// while(1) {sleep(1);}; sleep(seconds_to_run);
jack_deactivate(client); jack_client_close(client); }
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