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authorSteven Rostedt <srostedt@redhat.com>2009-03-30 11:11:28 -0400
committerIngo Molnar <mingo@elte.hu>2009-04-01 14:47:42 +0200
commit2aad1b76e6b0cc5a2e5d9b95a9f356ddddbfa8a9 (patch)
tree80ac6be0f1502079a50f8b1b4ffcc5e0586791e8 /kernel/trace
parent8b54e45b0005875f59cb8b1c44d429a161d5f245 (diff)
function-graph: allow unregistering twice
Impact: fix to permanent disabling of function graph tracer There should be nothing to prevent a tracer from unregistering a function graph callback more than once. This can simplify error paths. But currently, the counter does not account for mulitple unregistering of the function graph callback. If it happens, the function graph tracer will be permanently disabled. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/ftrace.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1752a63f37c..f1ed080406c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2719,6 +2719,9 @@ void unregister_ftrace_graph(void)
{
mutex_lock(&ftrace_lock);
+ if (!unlikely(atomic_read(&ftrace_graph_active)))
+ goto out;
+
atomic_dec(&ftrace_graph_active);
unregister_trace_sched_switch(ftrace_graph_probe_sched_switch);
ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
@@ -2726,6 +2729,7 @@ void unregister_ftrace_graph(void)
ftrace_shutdown(FTRACE_STOP_FUNC_RET);
unregister_pm_notifier(&ftrace_suspend_notifier);
+ out:
mutex_unlock(&ftrace_lock);
}