Messages in this thread | | | Date | Thu, 2 Dec 2004 07:46:20 -0800 | From | Andrew Burgess <> | Subject | Re: Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.31-19 |
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Ingo Molnar said:
>Florian Schmidt <mista.tapas@gmx.net> wrote: >> >> Hmm, i wonder if there's a way to detect non RT behaviour in jackd >> clients. I mean AFAIK the only thing allowed for the process callback >> of on is the FIFO it waits on to be woken, right? Every other sleeping >> is to be considered a bug.
>there's such a feature in -RT kernels. If a user process calls: > gettimeofday(1,1); >then the kernel turns 'atomic mode' on. To turn it off, call: > gettimeofday(1,0);
>while in atomic-mode, any non-atomic activity (scheduling) will produce >a kernel message and a SIGUSR2 sent to the offending process (once, >atomic mode has to be re-enabled again for the next message). Preemption >by a higher-prio task does not trigger a message/signal.
>If you run the client under gdb you should be able to catch the SIGUSR2 >signal and then you can see the offending code's backtrace via 'bt'.
Might be handy to have the option to send a SIGABRT, then you don't need to guess which app to run under gdb and the offending code is there in the core file.
Also, I'm cc-ing jack-devel. This could fit into libjack so no client mods would be needed I think. After the thread_init_callback is run libjack could run 'gettimeofday(1,1);' for each client thread. Then if any client breaks the rules you get a core showing where.
On further thought, I suppose libjack could install a SIGUSR2 handler and have that call abort for all the rt client threads. Still no client mods needed, only an RT-aware libjack.
A big thank you to Ingo and everyone else involved on behalf of all the linux audio users!
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