From: Prateek Sood prsood@codeaurora.org
commit 3a53acf1d9bea11b57c1f6205e3fe73f9d8a3688 upstream.
Task T2 Task T3 trace_options_core_write() subsystem_open()
mutex_lock(trace_types_lock) mutex_lock(event_mutex)
set_tracer_flag()
trace_event_enable_tgid_record() mutex_lock(trace_types_lock)
mutex_lock(event_mutex)
This gives a circular dependency deadlock between trace_types_lock and event_mutex. To fix this invert the usage of trace_types_lock and event_mutex in trace_options_core_write(). This keeps the sequence of lock usage consistent.
Link: http://lkml.kernel.org/r/0101016eef175e38-8ca71caf-a4eb-480d-a1e6-6f0bbc0154...
Cc: stable@vger.kernel.org Fixes: d914ba37d7145 ("tracing: Add support for recording tgid of tasks") Signed-off-by: Prateek Sood prsood@codeaurora.org Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/trace.c | 8 ++++++++ kernel/trace/trace_events.c | 8 ++++---- 2 files changed, 12 insertions(+), 4 deletions(-)
--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4590,6 +4590,10 @@ int trace_keep_overwrite(struct tracer *
int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled) { + if ((mask == TRACE_ITER_RECORD_TGID) || + (mask == TRACE_ITER_RECORD_CMD)) + lockdep_assert_held(&event_mutex); + /* do nothing if flag is already set */ if (!!(tr->trace_flags & mask) == !!enabled) return 0; @@ -4657,6 +4661,7 @@ static int trace_set_options(struct trac
cmp += len;
+ mutex_lock(&event_mutex); mutex_lock(&trace_types_lock);
ret = match_string(trace_options, -1, cmp); @@ -4667,6 +4672,7 @@ static int trace_set_options(struct trac ret = set_tracer_flag(tr, 1 << ret, !neg);
mutex_unlock(&trace_types_lock); + mutex_unlock(&event_mutex);
/* * If the first trailing whitespace is replaced with '\0' by strstrip, @@ -7972,9 +7978,11 @@ trace_options_core_write(struct file *fi if (val != 0 && val != 1) return -EINVAL;
+ mutex_lock(&event_mutex); mutex_lock(&trace_types_lock); ret = set_tracer_flag(tr, 1 << index, val); mutex_unlock(&trace_types_lock); + mutex_unlock(&event_mutex);
if (ret < 0) return ret; --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -320,7 +320,8 @@ void trace_event_enable_cmd_record(bool struct trace_event_file *file; struct trace_array *tr;
- mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + do_for_each_event_file(tr, file) {
if (!(file->flags & EVENT_FILE_FL_ENABLED)) @@ -334,7 +335,6 @@ void trace_event_enable_cmd_record(bool clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags); } } while_for_each_event_file(); - mutex_unlock(&event_mutex); }
void trace_event_enable_tgid_record(bool enable) @@ -342,7 +342,8 @@ void trace_event_enable_tgid_record(bool struct trace_event_file *file; struct trace_array *tr;
- mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + do_for_each_event_file(tr, file) { if (!(file->flags & EVENT_FILE_FL_ENABLED)) continue; @@ -356,7 +357,6 @@ void trace_event_enable_tgid_record(bool &file->flags); } } while_for_each_event_file(); - mutex_unlock(&event_mutex); }
static int __ftrace_event_enable_disable(struct trace_event_file *file,