Commit-ID: 2aad1b76e6b0cc5a2e5d9b95a9f356ddddbfa8a9
Gitweb: http://git.kernel.org/tip/2aad1b76e6b0cc5a2e5d9b95a9f356ddddbfa8a9
Author: Steven Rostedt <srostedt@xxxxxxxxxx>
AuthorDate: Mon, 30 Mar 2009 11:11:28 -0400
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 1 Apr 2009 14:47:42 +0200
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@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/trace/ftrace.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1752a63..f1ed080 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);
}
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