Messages in this thread Patch in this message | | | Date | Fri, 26 Jul 2013 09:03:36 -0400 | From | Steven Rostedt <> | Subject | [PATCH 9/9] tracing: Remove locking trace_types_lock from tracing_reset_all_online_cpus() |
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From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
Commit a82274151af "tracing: Protect ftrace_trace_arrays list in trace_events.c" added taking the trace_types_lock mutex in trace_events.c as there were several locations that needed it for protection. Unfortunately, it also encapsulated a call to tracing_reset_all_online_cpus() which also takes the trace_types_lock, causing a deadlock.
This happens when a module has tracepoints and has been traced. When the module is removed, the trace events module notifier will grab the trace_types_lock, do a bunch of clean ups, and also clears the buffer by calling tracing_reset_all_online_cpus. This doesn't happen often which explains why it wasn't caught right away.
Commit a82274151af was marked for stable, which means this must be sent to stable too.
Link: http://lkml.kernel.org/r/51EEC646.7070306@broadcom.com
Reported-by: Arend van Spril <arend@broadcom.com> Tested-by: Arend van Spriel <arend@broadcom.com> Cc: Alexander Z Lam <azl@google.com> Cc: Vaibhav Nagarnaik <vnagarnaik@google.com> Cc: David Sharp <dhsharp@google.com> Cc: stable@vger.kernel.org # 3.10 Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- kernel/trace/trace.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 69cba47..882ec1d 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1224,18 +1224,17 @@ void tracing_reset_current(int cpu) tracing_reset(&global_trace.trace_buffer, cpu); } +/* Must have trace_types_lock held */ void tracing_reset_all_online_cpus(void) { struct trace_array *tr; - mutex_lock(&trace_types_lock); list_for_each_entry(tr, &ftrace_trace_arrays, list) { tracing_reset_online_cpus(&tr->trace_buffer); #ifdef CONFIG_TRACER_MAX_TRACE tracing_reset_online_cpus(&tr->max_buffer); #endif } - mutex_unlock(&trace_types_lock); } #define SAVED_CMDLINES 128 -- 1.7.10.4
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