This is a note to let you know that I've just added the patch titled
ftrace: Initialize the ftrace profiler for each possible cpu
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ftrace-initialize-the-ftrace-profiler-for-each-possible-cpu.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From c4602c1c818bd6626178d6d3fcc152d9f2f48ac0 Mon Sep 17 00:00:00 2001
From: Miao Xie <[email protected]>
Date: Mon, 16 Dec 2013 15:20:01 +0800
Subject: ftrace: Initialize the ftrace profiler for each possible cpu
From: Miao Xie <[email protected]>
commit c4602c1c818bd6626178d6d3fcc152d9f2f48ac0 upstream.
Ftrace currently initializes only the online CPUs. This implementation has
two problems:
- If we online a CPU after we enable the function profile, and then run the
test, we will lose the trace information on that CPU.
Steps to reproduce:
# echo 0 > /sys/devices/system/cpu/cpu1/online
# cd <debugfs>/tracing/
# echo <some function name> >> set_ftrace_filter
# echo 1 > function_profile_enabled
# echo 1 > /sys/devices/system/cpu/cpu1/online
# run test
- If we offline a CPU before we enable the function profile, we will not clear
the trace information when we enable the function profile. It will trouble
the users.
Steps to reproduce:
# cd <debugfs>/tracing/
# echo <some function name> >> set_ftrace_filter
# echo 1 > function_profile_enabled
# run test
# cat trace_stat/function*
# echo 0 > /sys/devices/system/cpu/cpu1/online
# echo 0 > function_profile_enabled
# echo 1 > function_profile_enabled
# cat trace_stat/function*
# run test
# cat trace_stat/function*
So it is better that we initialize the ftrace profiler for each possible cpu
every time we enable the function profile instead of just the online ones.
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Miao Xie <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/trace/ftrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -775,7 +775,7 @@ static int ftrace_profile_init(void)
int cpu;
int ret = 0;
- for_each_online_cpu(cpu) {
+ for_each_possible_cpu(cpu) {
ret = ftrace_profile_init_cpu(cpu);
if (ret)
break;
Patches currently in stable-queue which might be from [email protected] are
queue-3.12/ftrace-initialize-the-ftrace-profiler-for-each-possible-cpu.patch
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