1 files changed, 20 insertions, 19 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index fa59fe8c02d5..278209c547a8 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -107,9 +107,6 @@ list_del_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
 
         list_del_init(&counter->list_entry);
 
-        if (list_empty(&counter->sibling_list))
-                return;
-
         /*
          * If this was a group counter with sibling counters then
          * upgrade the siblings to singleton counters by adding them
@@ -395,9 +392,6 @@ counter_sched_in(struct perf_counter *counter,
                  struct perf_counter_context *ctx,
                  int cpu)
 {
-        if (!counter->active)
-                return;
-
         hw_perf_counter_enable(counter);
         counter->active = 1;
         counter->oncpu = cpu;   /* TODO: put 'cpu' into cpuctx->cpu */
@@ -876,32 +870,39 @@ asmlinkage int sys_perf_counter_open(
                 return -EFAULT;
 
         /*
-         * Look up the group leader:
+         * Get the target context (task or percpu):
+         */
+        ctx = find_get_context(pid, cpu);
+        if (IS_ERR(ctx))
+                return PTR_ERR(ctx);
+
+        /*
+         * Look up the group leader (we will attach this counter to it):
          */
         group_leader = NULL;
         if (group_fd != -1) {
                 ret = -EINVAL;
                 group_file = fget_light(group_fd, &fput_needed);
                 if (!group_file)
-                        goto out_fput;
+                        goto err_put_context;
                 if (group_file->f_op != &perf_fops)
-                        goto out_fput;
+                        goto err_put_context;
 
                 group_leader = group_file->private_data;
                 /*
-                 * Do not allow a recursive hierarchy:
+                 * Do not allow a recursive hierarchy (this new sibling
+                 * becoming part of another group-sibling):
+                 */
+                if (group_leader->group_leader != group_leader)
+                        goto err_put_context;
+                /*
+                 * Do not allow to attach to a group in a different
+                 * task or CPU context:
                  */
-                if (group_leader->group_leader)
-                        goto out_fput;
+                if (group_leader->ctx != ctx)
+                        goto err_put_context;
         }
 
-        /*
-         * Get the target context (task or percpu):
-         */
-        ctx = find_get_context(pid, cpu);
-        if (IS_ERR(ctx))
-                return PTR_ERR(ctx);
-
         ret = -ENOMEM;
         counter = perf_counter_alloc(&hw_event, cpu, group_leader);
         if (!counter)