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Subject[PATCH 1/3] tracing: Fix race with update_max_tr_single and changing tracers
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

The commit 34600f0e9 "tracing: Fix race with max_tr and changing tracers"
fixed the updating of the main buffers with the race of changing
tracers, but left out the fix to the updating of just a per cpu buffer.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4f1dade..7ba7fc7 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -744,8 +744,11 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
return;

WARN_ON_ONCE(!irqs_disabled());
- if (WARN_ON_ONCE(!current_trace->allocated_snapshot))
+ if (!current_trace->allocated_snapshot) {
+ /* Only the nop tracer should hit this when disabling */
+ WARN_ON_ONCE(current_trace != &nop_trace);
return;
+ }

arch_spin_lock(&ftrace_max_lock);

--
1.7.10.4

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