Commit b07ef7741122a83575499c11417e514877941e76

Authored by Mandeep Singh Baines
Committed by Tejun Heo
1 parent 026085ef5a

cgroup: remove redundant get/put of task struct

threadgroup_lock() guarantees that the target threadgroup will
remain stable - no new task will be added, no new PF_EXITING
will be set and exec won't happen.

Changes in V2:
* https://lkml.org/lkml/2011/12/20/369 (Tejun Heo)
  * Undo incorrect removal of get/put from attach_task_by_pid()
* Author
  * Remove a comment which is made stale by this change

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: containers@lists.linux-foundation.org
Cc: cgroups@vger.kernel.org
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Menage <paul@paulmenage.org>

Showing 1 changed file with 2 additions and 9 deletions Side-by-side Diff

... ... @@ -2116,7 +2116,7 @@
2116 2116 retval = -EAGAIN;
2117 2117 goto out_free_group_list;
2118 2118 }
2119   - /* take a reference on each task in the group to go in the array. */
  2119 +
2120 2120 tsk = leader;
2121 2121 i = nr_migrating_tasks = 0;
2122 2122 do {
... ... @@ -2128,7 +2128,6 @@
2128 2128  
2129 2129 /* as per above, nr_threads may decrease, but not increase. */
2130 2130 BUG_ON(i >= group_size);
2131   - get_task_struct(tsk);
2132 2131 /*
2133 2132 * saying GFP_ATOMIC has no effect here because we did prealloc
2134 2133 * earlier, but it's good form to communicate our expectations.
... ... @@ -2150,7 +2149,7 @@
2150 2149 /* methods shouldn't be called if no task is actually migrating */
2151 2150 retval = 0;
2152 2151 if (!nr_migrating_tasks)
2153   - goto out_put_tasks;
  2152 + goto out_free_group_list;
2154 2153  
2155 2154 /*
2156 2155 * step 1: check that we can legitimately attach to the cgroup.
... ... @@ -2233,12 +2232,6 @@
2233 2232 if (ss->cancel_attach)
2234 2233 ss->cancel_attach(ss, cgrp, &tset);
2235 2234 }
2236   - }
2237   -out_put_tasks:
2238   - /* clean up the array of referenced threads in the group. */
2239   - for (i = 0; i < group_size; i++) {
2240   - tc = flex_array_get(group, i);
2241   - put_task_struct(tc->task);
2242 2235 }
2243 2236 out_free_group_list:
2244 2237 flex_array_free(group);