xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

ftrace: add ftrace_graph_stop()

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

10
arch/x86/kernel/ftrace.c
View File

@@ -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;
}