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authorLiming Wang <liming.wang@windriver.com>2008-12-02 10:33:08 +0800
committerIngo Molnar <mingo@elte.hu>2008-12-02 09:23:24 +0100
commit66eafebc1086014709dc38f52ddcb3d67d9b346c (patch)
tree10147e635d8d4d15d73cb23baa32a2357570eab0
parent222658e08f72cd539d01f3aabdc258c596f487e2 (diff)
function trace: fix a bug of single thread function trace
Impact: fix "no output from tracer" bug caused by ftrace_update_pid_func() When disabling single thread function trace using "echo -1 > set_ftrace_pid", the normal function trace has to restore to original function, otherwise the normal function trace will not work well. Without this commit, something like below: $ ps |grep 850 850 root 2556 S -/bin/sh $ echo 850 > /debug/tracing/set_ftrace_pid $ echo function > /debug/tracing/current_tracer $ echo 1 > /debug/tracing/tracing_enabled $ sleep 1 $ echo 0 > /debug/tracing/tracing_enabled $ cat /debug/tracing/trace_pipe |wc -l 59704 $ echo -1 > /debug/tracing/set_ftrace_pid $ echo 1 > /debug/tracing/tracing_enabled $ sleep 1 $ echo 0 > /debug/tracing/tracing_enabled $ more /debug/tracing/trace_pipe <====== nothing output now! it should output trace record. Signed-off-by: Liming Wang <liming.wang@windriver.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/trace/ftrace.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 08b536a2614..6d89ab46c6e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -243,10 +243,8 @@ static void ftrace_update_pid_func(void)
set_ftrace_pid_function(func);
func = ftrace_pid_func;
} else {
- if (func != ftrace_pid_func)
- goto out;
-
- set_ftrace_pid_function(func);
+ if (func == ftrace_pid_func)
+ func = ftrace_pid_function;
}
#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST