Commit 4dd2aea2 authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Steven Rostedt (Google)
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tracing/timerlat: Print stacktrace in the IRQ handler if needed 

If print_stack and stop_tracing_us are set, and stop_tracing_us is hit
with latency higher than or equal to print_stack, print the
stack at the IRQ handler as it is useful to define the root cause for
the IRQ latency.

Link: https://lkml.kernel.org/r/fd04530ce98ae9270e41bb124ee5bf67b05ecfed.1652175637.git.bristot@kernel.org



Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent aa748949

Documentation/trace/timerlat-tracer.rst

+3 −2
Original line number Diff line number Diff line
@@ -74,8 +74,9 @@ directory. The timerlat configs are: 
 - stop_tracing_total_us: stop the system tracing if a

   timer latency at the *thread* context is higher than the configured

   value happens. Writing 0 disables this option.

 - print_stack: save the stack of the IRQ occurrence, and print

   it after the *thread context* event".

 - print_stack: save the stack of the IRQ occurrence. The stack is printed

   after the *thread context* event, or at the IRQ handler if *stop_tracing_us*

   is hit.



timerlat and osnoise

----------------------------

kernel/trace/trace_osnoise.c

+13 −0
Original line number Diff line number Diff line
@@ -1580,6 +1580,19 @@ static enum hrtimer_restart timerlat_irq(struct hrtimer *timer) 


	if (osnoise_data.stop_tracing) {

		if (time_to_us(diff) >= osnoise_data.stop_tracing) {



			/*

			 * At this point, if stop_tracing is set and <= print_stack,

			 * print_stack is set and would be printed in the thread handler.

			 *

			 * Thus, print the stack trace as it is helpful to define the

			 * root cause of an IRQ latency.

			 */

			if (osnoise_data.stop_tracing <= osnoise_data.print_stack) {

				timerlat_save_stack(0);

				timerlat_dump_stack(time_to_us(diff));

			}



			osnoise_stop_tracing();

			notify_new_max_latency(diff);

		}