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authorDaniel Bristot de Oliveira <bristot@kernel.org>2022-05-10 11:45:24 +0200
committerSteven Rostedt (Google) <rostedt@goodmis.org>2022-05-26 21:13:00 -0400
commit4dd2aea24ed7613735664feadc9879d37f718c23 (patch)
tree69acae3a0763f90848c337899bbc37fb2dd79bab
parentaa748949b4e665f473bc5abdc5f66029cb5f5522 (diff)
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: Daniel Bristot de Oliveira <bristot@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
-rw-r--r--Documentation/trace/timerlat-tracer.rst5
-rw-r--r--kernel/trace/trace_osnoise.c13
2 files changed, 16 insertions, 2 deletions
diff --git a/Documentation/trace/timerlat-tracer.rst b/Documentation/trace/timerlat-tracer.rst
index 64d1fe6e9b93..d643c95c01eb 100644
--- a/Documentation/trace/timerlat-tracer.rst
+++ b/Documentation/trace/timerlat-tracer.rst
@@ -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
----------------------------
diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 6494ca27ea6f..9b204ee3c6f5 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -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);
}