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author | Masami Hiramatsu <mhiramat@kernel.org> | 2018-11-05 18:00:43 +0900 |
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committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-12-08 20:54:09 -0500 |
commit | fc800a10be26017f8f338bc8e500d48e3e6429d9 (patch) | |
tree | 2a64e2470385b62d91461a843bb94c7acaddc2b3 /kernel | |
parent | 547cd9eacd1c699c8d1fa77c95c6cdb33b2eba6a (diff) | |
download | linux-fc800a10be26017f8f338bc8e500d48e3e6429d9.tar.gz linux-fc800a10be26017f8f338bc8e500d48e3e6429d9.tar.bz2 linux-fc800a10be26017f8f338bc8e500d48e3e6429d9.zip |
tracing: Lock event_mutex before synth_event_mutex
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@devbox
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>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/trace/trace_events.c | 34 | ||||
-rw-r--r-- | kernel/trace/trace_events_hist.c | 24 |
2 files changed, 38 insertions, 20 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index f94be0c2827b..a3b157f689ee 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2305,11 +2305,11 @@ __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); @@ -2317,6 +2317,16 @@ 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; } @@ -2366,17 +2376,29 @@ 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 eb908ef2ecec..1670c65389fe 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -912,7 +912,7 @@ 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)); @@ -936,7 +936,7 @@ 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; } @@ -1013,12 +1013,10 @@ 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); } } @@ -1030,6 +1028,7 @@ 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); /* @@ -1102,8 +1101,6 @@ 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); @@ -1113,10 +1110,13 @@ 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]); @@ -1127,12 +1127,10 @@ 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) { @@ -1142,16 +1140,14 @@ 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; } |