From 66eafebc1086014709dc38f52ddcb3d67d9b346c Mon Sep 17 00:00:00 2001 From: Liming Wang Date: Tue, 2 Dec 2008 10:33:08 +0800 Subject: [PATCH] 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 Signed-off-by: Ingo Molnar --- kernel/trace/ftrace.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 08b536a2614e..6d89ab46c6e3 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 -- GitLab