summaryrefslogtreecommitdiff
path: root/kernel/trace
diff options
context:
space:
mode:
authorDaniel Bristot de Oliveira <bristot@kernel.org>2021-10-31 19:04:57 +0100
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2021-11-01 18:09:52 -0400
commitc3b6343c0dc4a76f838e25391f6f1cdb25cfbb8c (patch)
treec3edbb8f62444023f356ad0e9f5c0434726c7392 /kernel/trace
parent66df27f19f7dacae471f7214df5bab93d6f88b5f (diff)
tracing/osnoise: Improve comments about barrier need for NMI callbacks
trace_osnoise_callback_enabled is used by ftrace_nmi_enter/exit() to know when to call the NMI callback. The barrier is used to avoid having callbacks enabled before the resetting date during the start or to touch the values after stopping the tracer. Link: https://lkml.kernel.org/r/a413b8f14aa9312fbd1ba99f96225a8aed831053.1635702894.git.bristot@kernel.org Cc: Ingo Molnar <mingo@redhat.com> Cc: Tom Zanussi <zanussi@kernel.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Clark Williams <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Daniel Bristot de Oliveira <bristot@kernel.org> Cc: linux-rt-users@vger.kernel.org Cc: linux-trace-devel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace_osnoise.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index ceff407655a5..7d6be609d3dd 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1930,8 +1930,10 @@ static int __osnoise_tracer_start(struct trace_array *tr)
retval = osnoise_hook_events();
if (retval)
return retval;
+
/*
- * Make sure NMIs see reseted values.
+ * Make sure that ftrace_nmi_enter/exit() see reset values
+ * before enabling trace_osnoise_callback_enabled.
*/
barrier();
trace_osnoise_callback_enabled = true;
@@ -1966,6 +1968,10 @@ static void osnoise_tracer_stop(struct trace_array *tr)
return;
trace_osnoise_callback_enabled = false;
+ /*
+ * Make sure that ftrace_nmi_enter/exit() see
+ * trace_osnoise_callback_enabled as false before continuing.
+ */
barrier();
stop_per_cpu_kthreads();