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ftrace: add ftrace_graph_stop()

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Impact: new ftrace_graph_stop function

While developing more features of function graph, I hit a bug that
caused the WARN_ON to trigger in the prepare_ftrace_return function.
Well, it was hard for me to find out that was happening because the
bug would not print, it would just cause a hard lockup or reboot.
The reason is that it is not safe to call printk from this function.

Looking further, I also found that it calls unregister_ftrace_graph,
which grabs a mutex and calls kstop machine. This would definitely
lock the box up if it were to trigger.

This patch adds a fast and safe ftrace_graph_stop() which will
stop the function tracer. Then it is safe to call the WARN ON.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt
2008-12-02 23:50:02 -05:00
committed by Ingo Molnar
parent bb4304c71c
commit 14a866c567
3 changed files with 13 additions and 4 deletions
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5
kernel/trace/ftrace.c
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@@ -1769,5 +1769,10 @@ void ftrace_graph_exit_task(struct task_struct *t)
kfree(ret_stack);
}
void ftrace_graph_stop(void)
{
ftrace_stop();
}
#endif