diff options
| author | Steven Rostedt (Google) <rostedt@goodmis.org> | 2024-02-22 20:33:24 -0500 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2024-03-18 10:33:05 -0400 |
| commit | cca990c7b565af0dc61a8f647c00833453cf5bff (patch) | |
| tree | 4a0af7f7b91086e09ff48c5fe7e7790751bf673f | |
| parent | 70a6ed553f7d3504febac467cb4a0bae621ba3c6 (diff) | |
tracing: Fix snapshot counter going between two tracers that use it
Running the ftrace selftests caused the ring buffer mapping test to fail.
Investigating, I found that the snapshot counter would be incremented
every time a tracer that uses the snapshot is enabled even if the snapshot
was used by the previous tracer.
That is:
# cd /sys/kernel/tracing
# echo wakeup_rt > current_tracer
# echo wakeup_dl > current_tracer
# echo nop > current_tracer
would leave the snapshot counter at 1 and not zero. That's because the
enabling of wakeup_dl would increment the counter again but the setting
the tracer to nop would only decrement it once.
Do not arm the snapshot for a tracer if the previous tracer already had it
armed.
Link: https://lore.kernel.org/linux-trace-kernel/20240223013344.570525723@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Fixes: 16f7e48ffc53a ("tracing: Add snapshot refcount")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/trace.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a7c0dc0aaf14..1e1fd377a1cf 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6162,7 +6162,7 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf) tracing_disarm_snapshot(tr); } - if (t->use_max_tr) { + if (!had_max_tr && t->use_max_tr) { ret = tracing_arm_snapshot_locked(tr); if (ret) goto out; |