| From | Kamal Mostafa <> | Subject | [PATCH 3.8 072/166] ftrace: Initialize the ftrace profiler for each possible cpu | Date | Wed, 15 Jan 2014 13:51:26 -0800 |
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3.8.13.16 -stable review patch. If anyone has any objections, please let me know.
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From: Miao Xie <miaox@cn.fujitsu.com>
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/1387178401-10619-1-git-send-email-miaox@cn.fujitsu.com
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- kernel/trace/ftrace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 03dbc77..35d7565 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -720,7 +720,7 @@ 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; -- 1.8.3.2
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