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| author | Steven Rostedt <srostedt@redhat.com> | 2008-12-02 23:50:02 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-12-03 08:56:23 +0100 |
| commit | 14a866c567e040ccf6240d68b083dd1dbbde63e6 (patch) | |
| tree | 4e8d62ecc345d44e7cd45f973ffb931070637532 | |
| parent | bb4304c71c97bf727ec43cd2f195c2c237c27fd3 (diff) | |
| download | linux-14a866c567e040ccf6240d68b083dd1dbbde63e6.tar.gz linux-14a866c567e040ccf6240d68b083dd1dbbde63e6.tar.bz2 linux-14a866c567e040ccf6240d68b083dd1dbbde63e6.zip | |
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>
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 10 | ||||
| -rw-r--r-- | include/linux/ftrace.h | 2 | ||||
| -rw-r--r-- | kernel/trace/ftrace.c | 5 |
3 files changed, 13 insertions, 4 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 1a5b8f8cb3cc..adba8e9a427c 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; } diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index afba918c623c..58ca1c3a3f4d 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -376,6 +376,8 @@ typedef void (*trace_func_graph_ent_t)(struct ftrace_graph_ent *); /* entry */ extern int register_ftrace_graph(trace_func_graph_ret_t retfunc, trace_func_graph_ent_t entryfunc); +extern void ftrace_graph_stop(void); + /* The current handlers in use */ extern trace_func_graph_ret_t ftrace_graph_return; extern trace_func_graph_ent_t ftrace_graph_entry; diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 2e78628443e8..a44af05ae2d0 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1769,5 +1769,10 @@ void ftrace_graph_exit_task(struct task_struct *t) kfree(ret_stack); } + +void ftrace_graph_stop(void) +{ + ftrace_stop(); +} #endif |