Messages in this thread Patch in this message | | | Date | Wed, 01 Apr 2009 10:19:50 -0400 | From | Steven Rostedt <> | Subject | [PATCH 1/2] function-graph: allow unregistering twice |
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From: Steven Rostedt <srostedt@redhat.com>
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> --- 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); } -- 1.6.2.1 --
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