[alsa-devel] Can't detect "XRUNs"

[Raphaël Dingé]

Hi Takashi,

>> The recent kernel puts the xrun debug messages in trace buffer instead
>> of the kernel messages.  Try to enable the tracing in
>> /sys/kernel/debug/tracing/events/snd_pcm/xrun/enable, and watch the
>> trace buffer (/sys/kernel/debug/tracing/trace).
>
> Thanks for your very quick reply, I'll try this now.

I must do this wrong again.

So I kept echo 5 > /proc/asound/card2/pcm0p/xrun_debug
(not sure if still relevant with ftrace)

And I mounted tracefs
mount -t tracefs nodev /sys/kernel/tracing

And then I can
echo 1 > /sys/kernel/tracing/events/snd_pcm/xrun/enable

I can verify that
cat /sys/kernel/tracing/events/snd_pcm/xrun/enable gives 1
and all enable upper returns X

cat /sys/kernel/tracing/tracing_on is 1

But then
cat /sys/kernel/tracing/trace
Starts with # tracer: nop
and then the header for tracing, and that doesn't change over time.

No event gets logged.

Is tracer "nop" the right one?

As for my kernel configuration I have currently, regarding what seems
to be related to FTRACE :

CONFIG_NOP_TRACER=y
CONFIG_HAVE_FUNCTION_TRACER=y
CONFIG_HAVE_FUNCTION_GRAPH_TRACER=y
CONFIG_HAVE_DYNAMIC_FTRACE=y
CONFIG_HAVE_DYNAMIC_FTRACE_WITH_REGS=y
CONFIG_HAVE_FTRACE_MCOUNT_RECORD=y
CONFIG_HAVE_SYSCALL_TRACEPOINTS=y
CONFIG_HAVE_FENTRY=y
CONFIG_HAVE_C_RECORDMCOUNT=y
CONFIG_TRACE_CLOCK=y
CONFIG_RING_BUFFER=y
CONFIG_EVENT_TRACING=y
CONFIG_CONTEXT_SWITCH_TRACER=y
CONFIG_TRACING=y
CONFIG_GENERIC_TRACER=y
CONFIG_TRACING_SUPPORT=y
CONFIG_FTRACE=y
# CONFIG_FUNCTION_TRACER is not set
# CONFIG_PREEMPTIRQ_EVENTS is not set
# CONFIG_IRQSOFF_TRACER is not set
# CONFIG_SCHED_TRACER is not set
# CONFIG_HWLAT_TRACER is not set
# CONFIG_FTRACE_SYSCALLS is not set
# CONFIG_TRACER_SNAPSHOT is not set

I guess I might need to enable one of the config like FUNCTION_TRACER?

Sorry, I just started Linux, so my knowledge of it is very low.

Thanks,

Raphael