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Subject[PATCH 1/8] tracing: Fix initialization failure path in tracing_set_tracer()
Date
If tracer->init() fails, current code will leave current_tracer pointing
to an unusable tracer, which at best makes 'current_tracer' report
inaccurate value.

Fix the issue by pointing current_tracer to nop tracer, and only update
current_tracer with the new one after all the initialization succeeds.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 814ff30..954f7d7 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3183,10 +3183,10 @@ static int tracing_set_tracer(const char *buf)
}
destroy_trace_option_files(topts);

- current_trace = t;
+ current_trace = &nop_trace;

- topts = create_trace_option_files(current_trace);
- if (current_trace->use_max_tr) {
+ topts = create_trace_option_files(t);
+ if (t->use_max_tr) {
int cpu;
/* we need to make per cpu buffer sizes equivalent */
for_each_tracing_cpu(cpu) {
@@ -3206,6 +3206,7 @@ static int tracing_set_tracer(const char *buf)
goto out;
}

+ current_trace = t;
trace_branch_enable(tr);
out:
mutex_unlock(&trace_types_lock);
--
1.7.10.4


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