From 1603dda47714cebe8a29b2154407da7a929d13f4 Mon Sep 17 00:00:00 2001 From: Daniel Bristot de Oliveira Date: Fri, 9 Dec 2022 23:05:52 +0100 Subject: tracing/osnoise: Add PANIC_ON_STOP option Often the latency observed in a CPU is not caused by the work being done in the CPU itself, but by work done on another CPU that causes the hardware to stall all CPUs. In this case, it is interesting to know what is happening on ALL CPUs, and the best way to do this is via crash dump analysis. Add the PANIC_ON_STOP option to osnoise/timerlat tracers. The default behavior is having this option off. When enabled by the user, the system will panic after hitting a stop tracing condition. This option was motivated by a real scenario that Juri Lelli and I were debugging. Link: https://lkml.kernel.org/r/249ce4287c6725543e6db845a6e0df621dc67db5.1670623111.git.bristot@kernel.org Cc: Juri Lelli Cc: Clark Williams Cc: Bagas Sanjaya Cc: Daniel Bristot de Oliveira Cc: Masami Hiramatsu Cc: Jonathan Corbet Signed-off-by: Daniel Bristot de Oliveira Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace_osnoise.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'kernel/trace') diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index 8ba82c71268f..5a7613942223 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -54,10 +54,11 @@ enum osnoise_options_index { OSN_DEFAULTS = 0, OSN_WORKLOAD, + OSN_PANIC_ON_STOP, OSN_MAX }; -static const char * const osnoise_options_str[OSN_MAX] = { "DEFAULTS", "OSNOISE_WORKLOAD" }; +static const char * const osnoise_options_str[OSN_MAX] = { "DEFAULTS", "OSNOISE_WORKLOAD", "PANIC_ON_STOP" }; #define OSN_DEFAULT_OPTIONS 0x2 static unsigned long osnoise_options = OSN_DEFAULT_OPTIONS; @@ -1270,6 +1271,9 @@ static __always_inline void osnoise_stop_tracing(void) trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_, "stop tracing hit on cpu %d\n", smp_processor_id()); + if (test_bit(OSN_PANIC_ON_STOP, &osnoise_options)) + panic("tracer hit stop condition on CPU %d\n", smp_processor_id()); + tracer_tracing_off(tr); } rcu_read_unlock(); -- cgit v1.2.3