Merge branch 'perf/urgent' into perf/core, to pick up fixes

[sfrench/cifs-2.6.git] / kernel / events / core.c

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2d7990d4e9884ce9cf0b2e51676c96b362097afc..6e75a5c9412dee17daabc1cb131bb517ad431207 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4261,7 +4261,7 @@ int perf_event_release_kernel(struct perf_event *event)
 
        raw_spin_lock_irq(&ctx->lock);
        /*
-        * Mark this even as STATE_DEAD, there is no external reference to it
+        * Mark this event as STATE_DEAD, there is no external reference to it
         * anymore.
         *
         * Anybody acquiring event->child_mutex after the below loop _must_
@@ -10556,21 +10556,22 @@ void perf_event_free_task(struct task_struct *task)
                        continue;
 
                mutex_lock(&ctx->mutex);
-again:
-               list_for_each_entry_safe(event, tmp, &ctx->pinned_groups,
-                               group_entry)
-                       perf_free_event(event, ctx);
+               raw_spin_lock_irq(&ctx->lock);
+               /*
+                * Destroy the task <-> ctx relation and mark the context dead.
+                *
+                * This is important because even though the task hasn't been
+                * exposed yet the context has been (through child_list).
+                */
+               RCU_INIT_POINTER(task->perf_event_ctxp[ctxn], NULL);
+               WRITE_ONCE(ctx->task, TASK_TOMBSTONE);
+               put_task_struct(task); /* cannot be last */
+               raw_spin_unlock_irq(&ctx->lock);
 
-               list_for_each_entry_safe(event, tmp, &ctx->flexible_groups,
-                               group_entry)
+               list_for_each_entry_safe(event, tmp, &ctx->event_list, event_entry)
                        perf_free_event(event, ctx);
 
-               if (!list_empty(&ctx->pinned_groups) ||
-                               !list_empty(&ctx->flexible_groups))
-                       goto again;
-
                mutex_unlock(&ctx->mutex);
-
                put_ctx(ctx);
        }
 }
@@ -10608,7 +10609,12 @@ const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
 }
 
 /*
- * inherit a event from parent task to child task:
+ * Inherit a event from parent task to child task.
+ *
+ * Returns:
+ *  - valid pointer on success
+ *  - NULL for orphaned events
+ *  - IS_ERR() on error
  */
 static struct perf_event *
 inherit_event(struct perf_event *parent_event,
@@ -10702,6 +10708,16 @@ inherit_event(struct perf_event *parent_event,
        return child_event;
 }
 
+/*
+ * Inherits an event group.
+ *
+ * This will quietly suppress orphaned events; !inherit_event() is not an error.
+ * This matches with perf_event_release_kernel() removing all child events.
+ *
+ * Returns:
+ *  - 0 on success
+ *  - <0 on error
+ */
 static int inherit_group(struct perf_event *parent_event,
              struct task_struct *parent,
              struct perf_event_context *parent_ctx,
@@ -10716,6 +10732,11 @@ static int inherit_group(struct perf_event *parent_event,
                                 child, NULL, child_ctx);
        if (IS_ERR(leader))
                return PTR_ERR(leader);
+       /*
+        * @leader can be NULL here because of is_orphaned_event(). In this
+        * case inherit_event() will create individual events, similar to what
+        * perf_group_detach() would do anyway.
+        */
        list_for_each_entry(sub, &parent_event->sibling_list, group_entry) {
                child_ctr = inherit_event(sub, parent, parent_ctx,
                                            child, leader, child_ctx);
@@ -10725,6 +10746,17 @@ static int inherit_group(struct perf_event *parent_event,
        return 0;
 }
 
+/*
+ * Creates the child task context and tries to inherit the event-group.
+ *
+ * Clears @inherited_all on !attr.inherited or error. Note that we'll leave
+ * inherited_all set when we 'fail' to inherit an orphaned event; this is
+ * consistent with perf_event_release_kernel() removing all child events.
+ *
+ * Returns:
+ *  - 0 on success
+ *  - <0 on error
+ */
 static int
 inherit_task_group(struct perf_event *event, struct task_struct *parent,
                   struct perf_event_context *parent_ctx,
@@ -10747,7 +10779,6 @@ inherit_task_group(struct perf_event *event, struct task_struct *parent,
                 * First allocate and initialize a context for the
                 * child.
                 */
-
                child_ctx = alloc_perf_context(parent_ctx->pmu, child);
                if (!child_ctx)
                        return -ENOMEM;
@@ -10809,7 +10840,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
                ret = inherit_task_group(event, parent, parent_ctx,
                                         child, ctxn, &inherited_all);
                if (ret)
-                       break;
+                       goto out_unlock;
        }
 
        /*
@@ -10825,7 +10856,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
                ret = inherit_task_group(event, parent, parent_ctx,
                                         child, ctxn, &inherited_all);
                if (ret)
-                       break;
+                       goto out_unlock;
        }
 
        raw_spin_lock_irqsave(&parent_ctx->lock, flags);
@@ -10853,6 +10884,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
        }
 
        raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
+out_unlock:
        mutex_unlock(&parent_ctx->mutex);
 
        perf_unpin_context(parent_ctx);