diff options
author | KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> | 2009-03-06 15:29:04 +0900 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2009-03-06 12:07:38 +0100 |
commit | 10dd3ebe213c31bff14b4dae3c5d32a76b1fad7c (patch) | |
tree | 251609d532ccbb4c157a2c5c3d7a5b8176eeab8c /kernel | |
parent | 422d3c7a577b15e1384c9d4e72a9540896b685fa (diff) |
tracing: fix deadlock when setting set_ftrace_pid
Impact: fix deadlock while using set_ftrace_pid
Reproducer:
# cd /sys/kernel/debug/tracing
# echo $$ > set_ftrace_pid
then, console becomes hung.
Details:
when writing set_ftracepid, kernel callstack is following
ftrace_pid_write()
mutex_lock(&ftrace_lock);
ftrace_update_pid_func()
mutex_lock(&ftrace_lock);
mutex_unlock(&ftrace_lock);
mutex_unlock(&ftrace_lock);
then, system always deadlocks when ftrace_pid_write() is called.
In past days, ftrace_pid_write() used ftrace_start_lock, but
commit e6ea44e9b4c12325337cd1c06103cd515a1c02b2 consolidated
ftrace_start_lock to ftrace_lock.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <srostedt@redhat.com>
LKML-Reference: <20090306151155.0778.A69D9226@jp.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/trace/ftrace.c | 7 |
1 files changed, 1 insertions, 6 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index d7a06a0d944..d33d306bdcf 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -218,10 +218,8 @@ static void ftrace_update_pid_func(void) { ftrace_func_t func; - mutex_lock(&ftrace_lock); - if (ftrace_trace_function == ftrace_stub) - goto out; + return; func = ftrace_trace_function; @@ -238,9 +236,6 @@ static void ftrace_update_pid_func(void) #else __ftrace_trace_function = func; #endif - - out: - mutex_unlock(&ftrace_lock); } /* set when tracing only a pid */ |