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authorSteven Rostedt <srostedt@redhat.com>2008-12-02 23:50:02 -0500
committerIngo Molnar <mingo@elte.hu>2008-12-03 08:56:23 +0100
commit14a866c567e040ccf6240d68b083dd1dbbde63e6 (patch)
tree4e8d62ecc345d44e7cd45f973ffb931070637532 /arch/x86
parentbb4304c71c97bf727ec43cd2f195c2c237c27fd3 (diff)
ftrace: add ftrace_graph_stop()
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>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/ftrace.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 1a5b8f8cb3c..adba8e9a427 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -484,14 +484,16 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
: "memory"
);
- if (WARN_ON(faulted)) {
- unregister_ftrace_graph();
+ if (unlikely(faulted)) {
+ ftrace_graph_stop();
+ WARN_ON(1);
return;
}
- if (WARN_ON(!__kernel_text_address(old))) {
- unregister_ftrace_graph();
+ if (unlikely(!__kernel_text_address(old))) {
+ ftrace_graph_stop();
*parent = old;
+ WARN_ON(1);
return;
}