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authorPeter Zijlstra <peterz@infradead.org>2018-01-09 13:10:30 +0100
committerIngo Molnar <mingo@kernel.org>2018-01-25 14:48:29 +0100
commit82d94856fa221b5173eefd56bcd1057c037e9b07 (patch)
tree1e798ac4fd09b470a3c45e393048afab7ddb21bf /kernel
parent1f07476ec143bbed7bf0b641749783b1094b4c4f (diff)
perf/core: Fix lock inversion between perf,trace,cpuhp
Lockdep gifted us with noticing the following 4-way lockup scenario: perf_trace_init() #0 mutex_lock(&event_mutex) perf_trace_event_init() perf_trace_event_reg() tp_event->class->reg() := tracepoint_probe_register #1 mutex_lock(&tracepoints_mutex) trace_point_add_func() #2 static_key_enable() #2 do_cpu_up() perf_event_init_cpu() #3 mutex_lock(&pmus_lock) #4 mutex_lock(&ctx->mutex) perf_event_task_disable() mutex_lock(&current->perf_event_mutex) #4 ctx = perf_event_ctx_lock() #5 perf_event_for_each_child() do_exit() task_work_run() __fput() perf_release() perf_event_release_kernel() #4 mutex_lock(&ctx->mutex) #5 mutex_lock(&event->child_mutex) free_event() _free_event() event->destroy() := perf_trace_destroy #0 mutex_lock(&event_mutex); Fix that by moving the free_event() out from under the locks. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Steven Rostedt (VMware) <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4df5b695bf0d..2d80824298a7 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1231,6 +1231,10 @@ static void put_ctx(struct perf_event_context *ctx)
* perf_event_context::lock
* perf_event::mmap_mutex
* mmap_sem
+ *
+ * cpu_hotplug_lock
+ * pmus_lock
+ * cpuctx->mutex / perf_event_context::mutex
*/
static struct perf_event_context *
perf_event_ctx_lock_nested(struct perf_event *event, int nesting)
@@ -4196,6 +4200,7 @@ int perf_event_release_kernel(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
struct perf_event *child, *tmp;
+ LIST_HEAD(free_list);
/*
* If we got here through err_file: fput(event_file); we will not have
@@ -4268,8 +4273,7 @@ again:
struct perf_event, child_list);
if (tmp == child) {
perf_remove_from_context(child, DETACH_GROUP);
- list_del(&child->child_list);
- free_event(child);
+ list_move(&child->child_list, &free_list);
/*
* This matches the refcount bump in inherit_event();
* this can't be the last reference.
@@ -4284,6 +4288,11 @@ again:
}
mutex_unlock(&event->child_mutex);
+ list_for_each_entry_safe(child, tmp, &free_list, child_list) {
+ list_del(&child->child_list);
+ free_event(child);
+ }
+
no_ctx:
put_event(event); /* Must be the 'last' reference */
return 0;