[for-linus][PATCH 05/11] tracing/osnoise: Use built-in RCU list checking

Steven Rostedt
2023-01-25T16:20:21Z

From: Chuang Wang <nashuiliang@gmail.com>

list_for_each_entry_rcu() has built-in RCU and lock checking.

Pass cond argument to list_for_each_entry_rcu() to silence false lockdep
warning when CONFIG_PROVE_RCU_LIST is enabled.

Execute as follow:

[tracing]# echo osnoise > current_tracer
[tracing]# echo 1 > tracing_on
[tracing]# echo 0 > tracing_on

The trace_types_lock is held when osnoise_tracer_stop() or
timerlat_tracer_stop() are called in the non-RCU read side section.
So, pass lockdep_is_held(&trace_types_lock) to silence false lockdep
warning.

Link: https://lkml.kernel.org/r/20221227023036.784337-1-nashuiliang@gmail.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: dae181349f1e ("tracing/osnoise: Support a list of trace_array *tr")
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace_osnoise.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 94c1b5eb1dc0..210e1f168392 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -147,9 +147,8 @@ static void osnoise_unregister_instance(struct trace_array *tr)
* register/unregister serialization is provided by trace's
* trace_types_lock.
*/
- lockdep_assert_held(&trace_types_lock);
-
- list_for_each_entry_rcu(inst, &osnoise_instances, list) {
+ list_for_each_entry_rcu(inst, &osnoise_instances, list,
+ lockdep_is_held(&trace_types_lock)) {
if (inst->tr == tr) {
list_del_rcu(&inst->list);
found = 1;
--
2.39.0