tracing/branch-tracer: fix a trace recursion on branch tracer

Impact: fix crash when enabling the branch-tracer

When the branch tracer inserts an event through
probe_likely_condition(), it calls local_irq_save() and then results
in a trace recursion.

local_irq_save() -> trace_hardirqs_off() -> trace_hardirqs_off_caller()
	-> unlikely()

The trace_branch.c file is protected by DISABLE_BRANCH_PROFILING but
that doesn't prevent from external call to functions that use
unlikely().

My box crashed each time I tried to set this tracer (sudden and hard
reboot).

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 85265553918f266698e7136e2ca828e9ca33ce10..2511e32572cacfb903083370db5120ad8f3a058c 100644 (file)
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -41,7 +41,7 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
        if (unlikely(!tr))
                return;
 
-       local_irq_save(flags);
+       raw_local_irq_save(flags);
        cpu = raw_smp_processor_id();
        if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
                goto out;
@@ -73,7 +73,7 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 
  out:
        atomic_dec(&tr->data[cpu]->disabled);
-       local_irq_restore(flags);
+       raw_local_irq_restore(flags);
 }
 
 static inline