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tracing/function-return-tracer: add a barrier to ensure return stack index is incremented in memory

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Impact: fix possible race condition in ftrace function return tracer

This fixes a possible race condition if index incrementation
is not immediately flushed in memory.

Thanks for Andi Kleen and Steven Rostedt for pointing out this issue
and give me this solution.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker 2008-11-15 02:37:44 +01:00 committed by Ingo Molnar
parent 985809608f
commit b01c746617
1 changed files with 1 additions and 0 deletions
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arch/x86/kernel/ftrace.c
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@ -56,6 +56,7 @@ static int push_return_trace(unsigned long ret, unsigned long long time,
return -EBUSY;
index = ++ti->curr_ret_stack;
barrier();
ti->ret_stack[index].ret = ret;
ti->ret_stack[index].func = func;
ti->ret_stack[index].calltime = time;