On Mon, 18 Jul 2022 12:02:26 -0700
Arun Easi <aeasi@xxxxxxxxxxx> wrote:
> Many times when a problem was reported on the driver, we had to request
> for a repro with extended error logging (via driver module parameter)
> turned on. With this internal tracing in place, log messages that appear
> only with extended error logging are captured by default in the internal
> trace buffer.
>
> AFAIK, kernel tracing requires a user initiated action to be turned on,
> like enabling individual tracepoints. Though a script (either startup or
> udev) can do this job, enabling tracepoints by default for a single
> driver, I think, may not be a preferred choice -- particularly when the
> trace buffer is shared across the kernel. That also brings the extra
> overhead of finding how this could be done across various distros.
>
> For cases where the memory/driver size matters, there is an option to
> compile out this feature, plus choosing a lower default trace buffer size.
You can enable an ftrace instance from inside the kernel, and make it a
compile time option.
#include <linux/trace_events.h>
#include <linux/trace.h>
struct trace_array *tr;
tr = trace_array_get_by_name("qla2xxx");
trace_array_set_clr_event(tr, "qla", NULL, true);
And now you have trace events running:
# cat /sys/kernel/tracing/instances/qla/trace
-- Steve
