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

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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>
This commit is contained in:
Frederic Weisbecker
2008-11-16 05:59:52 +01:00
committed by Ingo Molnar
parent c91add5fa6
commit 072b40a156
1 changed files with 2 additions and 2 deletions
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4
kernel/trace/trace_branch.c
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@@ -41,7 +41,7 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
if (unlikely(!tr)) if (unlikely(!tr))
return; return;
local_irq_save(flags); raw_local_irq_save(flags);
cpu = raw_smp_processor_id(); cpu = raw_smp_processor_id();
if (atomic_inc_return(&tr->data[cpu]->disabled) != 1) if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
goto out; goto out;
@@ -73,7 +73,7 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
out: out:
atomic_dec(&tr->data[cpu]->disabled); atomic_dec(&tr->data[cpu]->disabled);
local_irq_restore(flags); raw_local_irq_restore(flags);
} }
static inline static inline