4 files changed, 37 insertions, 14 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 81aa3a4ece9f..1a3bf48743ce 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -913,10 +913,30 @@ static void put_ctx(struct perf_event_context *ctx)
  * Those places that change perf_event::ctx will hold both
  * perf_event_ctx::mutex of the 'old' and 'new' ctx value.
  *
- * Lock ordering is by mutex address. There is one other site where
- * perf_event_context::mutex nests and that is put_event(). But remember that
- * that is a parent<->child context relation, and migration does not affect
- * children, therefore these two orderings should not interact.
+ * Lock ordering is by mutex address. There are two other sites where
+ * perf_event_context::mutex nests and those are:
+ *
+ *  - perf_event_exit_task_context()    [ child , 0 ]
+ *      __perf_event_exit_task()
+ *        sync_child_event()
+ *          put_event()                 [ parent, 1 ]
+ *
+ *  - perf_event_init_context()         [ parent, 0 ]
+ *      inherit_task_group()
+ *        inherit_group()
+ *          inherit_event()
+ *            perf_event_alloc()
+ *              perf_init_event()
+ *                perf_try_init_event() [ child , 1 ]
+ *
+ * While it appears there is an obvious deadlock here -- the parent and child
+ * nesting levels are inverted between the two. This is in fact safe because
+ * life-time rules separate them. That is an exiting task cannot fork, and a
+ * spawning task cannot (yet) exit.
+ *
+ * But remember that that these are parent<->child context relations, and
+ * migration does not affect children, therefore these two orderings should not
+ * interact.
  *
  * The change in perf_event::ctx does not affect children (as claimed above)
  * because the sys_perf_event_open() case will install a new event and break
@@ -3657,9 +3677,6 @@ static void perf_remove_from_owner(struct perf_event *event)
         }
 }
 
-/*
- * Called when the last reference to the file is gone.
- */
 static void put_event(struct perf_event *event)
 {
         struct perf_event_context *ctx;
@@ -3697,6 +3714,9 @@ int perf_event_release_kernel(struct perf_event *event)
 }
 EXPORT_SYMBOL_GPL(perf_event_release_kernel);
 
+/*
+ * Called when the last reference to the file is gone.
+ */
 static int perf_release(struct inode *inode, struct file *file)
 {
         put_event(file->private_data);
@@ -7364,7 +7384,12 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
                 return -ENODEV;
 
         if (event->group_leader != event) {
-                ctx = perf_event_ctx_lock(event->group_leader);
+                /*
+                 * This ctx->mutex can nest when we're called through
+                 * inheritance. See the perf_event_ctx_lock_nested() comment.
+                 */
+                ctx = perf_event_ctx_lock_nested(event->group_leader,
+                                                 SINGLE_DEPTH_NESTING);
                 BUG_ON(!ctx);
         }
 
diff --git a/kernel/irq/dummychip.c b/kernel/irq/dummychip.c
index 988dc58e8847..2feb6feca0cc 100644
--- a/kernel/irq/dummychip.c
+++ b/kernel/irq/dummychip.c
@@ -57,5 +57,6 @@ struct irq_chip dummy_irq_chip = {
         .irq_ack        = noop,
         .irq_mask       = noop,
         .irq_unmask     = noop,
+        .flags          = IRQCHIP_SKIP_SET_WAKE,
 };
 EXPORT_SYMBOL_GPL(dummy_irq_chip);
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 11dc22a6983b..637a09461c1d 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -117,11 +117,7 @@ static int __clockevents_set_state(struct clock_event_device *dev,
         /* Transition with new state-specific callbacks */
         switch (state) {
         case CLOCK_EVT_STATE_DETACHED:
-                /*
-                 * This is an internal state, which is guaranteed to go from
-                 * SHUTDOWN to DETACHED. No driver interaction required.
-                 */
-                return 0;
+                /* The clockevent device is getting replaced. Shut it down. */
 
         case CLOCK_EVT_STATE_SHUTDOWN:
                 return dev->set_state_shutdown(dev);
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 692bf7184c8c..25a086bcb700 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -178,12 +178,13 @@ ftrace_print_hex_seq(struct trace_seq *p, const unsigned char *buf, int buf_len)
 EXPORT_SYMBOL(ftrace_print_hex_seq);
 
 const char *
-ftrace_print_array_seq(struct trace_seq *p, const void *buf, int buf_len,
+ftrace_print_array_seq(struct trace_seq *p, const void *buf, int count,
                        size_t el_size)
 {
         const char *ret = trace_seq_buffer_ptr(p);
         const char *prefix = "";
         void *ptr = (void *)buf;
+        size_t buf_len = count * el_size;
 
         trace_seq_putc(p, '{');