From: Masami Hiramatsu mhiramat@kernel.org
[ Upstream commit fc800a10be26017f8f338bc8e500d48e3e6429d9 ]
synthetic event is using synth_event_mutex for protecting synth_event_list, and event_trigger_write() path acquires locks as below order.
event_trigger_write(event_mutex) ->trigger_process_regex(trigger_cmd_mutex) ->event_hist_trigger_func(synth_event_mutex)
On the other hand, synthetic event creation and deletion paths call trace_add_event_call() and trace_remove_event_call() which acquires event_mutex. In that case, if we keep the synth_event_mutex locked while registering/unregistering synthetic events, its dependency will be inversed.
To avoid this issue, current synthetic event is using a 2 phase process to create/delete events. For example, it searches existing events under synth_event_mutex to check for event-name conflicts, and unlocks synth_event_mutex, then registers a new event under event_mutex locked. Finally, it locks synth_event_mutex and tries to add the new event to the list. But it can introduce complexity and a chance for name conflicts.
To solve this simpler, this introduces trace_add_event_call_nolock() and trace_remove_event_call_nolock() which don't acquire event_mutex inside. synthetic event can lock event_mutex before synth_event_mutex to solve the lock dependency issue simpler.
Link: http://lkml.kernel.org/r/154140844377.17322.13781091165954002713.stgit@devbo...
Reviewed-by: Tom Zanussi tom.zanussi@linux.intel.com Tested-by: Tom Zanussi tom.zanussi@linux.intel.com Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/trace_events.h | 2 ++ kernel/trace/trace_events.c | 34 ++++++++++++++++++++++++++------ kernel/trace/trace_events_hist.c | 24 ++++++++++------------ 3 files changed, 40 insertions(+), 20 deletions(-)
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 78a010e19ed41..0643c083ed862 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -529,6 +529,8 @@ extern int trace_event_raw_init(struct trace_event_call *call); extern int trace_define_field(struct trace_event_call *call, const char *type, const char *name, int offset, int size, int is_signed, int filter_type); +extern int trace_add_event_call_nolock(struct trace_event_call *call); +extern int trace_remove_event_call_nolock(struct trace_event_call *call); extern int trace_add_event_call(struct trace_event_call *call); extern int trace_remove_event_call(struct trace_event_call *call); extern int trace_event_get_offsets(struct trace_event_call *call); diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 7345f5f8f3fe6..017f737237e60 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2302,11 +2302,11 @@ __trace_early_add_new_event(struct trace_event_call *call, struct ftrace_module_file_ops; static void __add_event_to_tracers(struct trace_event_call *call);
-/* Add an additional event_call dynamically */ -int trace_add_event_call(struct trace_event_call *call) +int trace_add_event_call_nolock(struct trace_event_call *call) { int ret; - mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + mutex_lock(&trace_types_lock);
ret = __register_event(call, NULL); @@ -2314,6 +2314,16 @@ int trace_add_event_call(struct trace_event_call *call) __add_event_to_tracers(call);
mutex_unlock(&trace_types_lock); + return ret; +} + +/* Add an additional event_call dynamically */ +int trace_add_event_call(struct trace_event_call *call) +{ + int ret; + + mutex_lock(&event_mutex); + ret = trace_add_event_call_nolock(call); mutex_unlock(&event_mutex); return ret; } @@ -2363,17 +2373,29 @@ static int probe_remove_event_call(struct trace_event_call *call) return 0; }
-/* Remove an event_call */ -int trace_remove_event_call(struct trace_event_call *call) +/* no event_mutex version */ +int trace_remove_event_call_nolock(struct trace_event_call *call) { int ret;
- mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + mutex_lock(&trace_types_lock); down_write(&trace_event_sem); ret = probe_remove_event_call(call); up_write(&trace_event_sem); mutex_unlock(&trace_types_lock); + + return ret; +} + +/* Remove an event_call */ +int trace_remove_event_call(struct trace_event_call *call) +{ + int ret; + + mutex_lock(&event_mutex); + ret = trace_remove_event_call_nolock(call); mutex_unlock(&event_mutex);
return ret; diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index dac518977e7d0..11d952650fa72 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -914,7 +914,7 @@ static int register_synth_event(struct synth_event *event) call->data = event; call->tp = event->tp;
- ret = trace_add_event_call(call); + ret = trace_add_event_call_nolock(call); if (ret) { pr_warn("Failed to register synthetic event: %s\n", trace_event_name(call)); @@ -938,7 +938,7 @@ static int unregister_synth_event(struct synth_event *event) struct trace_event_call *call = &event->call; int ret;
- ret = trace_remove_event_call(call); + ret = trace_remove_event_call_nolock(call);
return ret; } @@ -1015,12 +1015,10 @@ static void add_or_delete_synth_event(struct synth_event *event, int delete) if (delete) free_synth_event(event); else { - mutex_lock(&synth_event_mutex); if (!find_synth_event(event->name)) list_add(&event->list, &synth_event_list); else free_synth_event(event); - mutex_unlock(&synth_event_mutex); } }
@@ -1032,6 +1030,7 @@ static int create_synth_event(int argc, char **argv) int i, consumed = 0, n_fields = 0, ret = 0; char *name;
+ mutex_lock(&event_mutex); mutex_lock(&synth_event_mutex);
/* @@ -1104,8 +1103,6 @@ static int create_synth_event(int argc, char **argv) goto err; } out: - mutex_unlock(&synth_event_mutex); - if (event) { if (delete_event) { ret = unregister_synth_event(event); @@ -1115,10 +1112,13 @@ static int create_synth_event(int argc, char **argv) add_or_delete_synth_event(event, ret); } } + mutex_unlock(&synth_event_mutex); + mutex_unlock(&event_mutex);
return ret; err: mutex_unlock(&synth_event_mutex); + mutex_unlock(&event_mutex);
for (i = 0; i < n_fields; i++) free_synth_field(fields[i]); @@ -1129,12 +1129,10 @@ static int create_synth_event(int argc, char **argv)
static int release_all_synth_events(void) { - struct list_head release_events; struct synth_event *event, *e; int ret = 0;
- INIT_LIST_HEAD(&release_events); - + mutex_lock(&event_mutex); mutex_lock(&synth_event_mutex);
list_for_each_entry(event, &synth_event_list, list) { @@ -1144,16 +1142,14 @@ static int release_all_synth_events(void) } }
- list_splice_init(&event->list, &release_events); - - mutex_unlock(&synth_event_mutex); - - list_for_each_entry_safe(event, e, &release_events, list) { + list_for_each_entry_safe(event, e, &synth_event_list, list) { list_del(&event->list);
ret = unregister_synth_event(event); add_or_delete_synth_event(event, !ret); } + mutex_unlock(&synth_event_mutex); + mutex_unlock(&event_mutex);
return ret; }