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>

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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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10

arch/x86/kernel/ftrace.c

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2

include/linux/ftrace.h

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5

kernel/trace/ftrace.c

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