Commit e8d55fdeb882cfcb5e8db5a5ce16edfba78aafc5
Committed by
Linus Torvalds
Linus Torvalds
1 parent
472b1053f3
Exists in
master
and in
4 other branches
cgroups: simplify init_subsys()
We are at system boot and there is only 1 cgroup group (i,e, init_css_set), so
we don't need to run through the css_set linked list. Neither do we need to
run through the task list, since no processes have been created yet.
Also referring to a comment in cgroup.h:
struct css_set
{
...
/*
* Set of subsystem states, one for each subsystem. This array
* is immutable after creation apart from the init_css_set
* during subsystem registration (at boot time).
*/
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
}
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Reviewed-by: Paul Menage <menage@google.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Showing 2 changed files with 10 additions and 28 deletions Side-by-side Diff
Documentation/cgroups.txt
| ... | ... | @@ -500,8 +500,7 @@ |
| 500 | 500 | |
| 501 | 501 | void fork(struct cgroup_subsy *ss, struct task_struct *task) |
| 502 | 502 | |
| 503 | -Called when a task is forked into a cgroup. Also called during | |
| 504 | -registration for all existing tasks. | |
| 503 | +Called when a task is forked into a cgroup. | |
| 505 | 504 | |
| 506 | 505 | void exit(struct cgroup_subsys *ss, struct task_struct *task) |
| 507 | 506 |
kernel/cgroup.c
| ... | ... | @@ -2477,7 +2477,6 @@ |
| 2477 | 2477 | static void __init cgroup_init_subsys(struct cgroup_subsys *ss) |
| 2478 | 2478 | { |
| 2479 | 2479 | struct cgroup_subsys_state *css; |
| 2480 | - struct list_head *l; | |
| 2481 | 2480 | |
| 2482 | 2481 | printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name); |
| 2483 | 2482 | |
| 2484 | 2483 | |
| 2485 | 2484 | |
| 2486 | 2485 | |
| ... | ... | @@ -2488,34 +2487,18 @@ |
| 2488 | 2487 | BUG_ON(IS_ERR(css)); |
| 2489 | 2488 | init_cgroup_css(css, ss, dummytop); |
| 2490 | 2489 | |
| 2491 | - /* Update all cgroup groups to contain a subsys | |
| 2490 | + /* Update the init_css_set to contain a subsys | |
| 2492 | 2491 | * pointer to this state - since the subsystem is |
| 2493 | - * newly registered, all tasks and hence all cgroup | |
| 2494 | - * groups are in the subsystem's top cgroup. */ | |
| 2495 | - write_lock(&css_set_lock); | |
| 2496 | - l = &init_css_set.list; | |
| 2497 | - do { | |
| 2498 | - struct css_set *cg = | |
| 2499 | - list_entry(l, struct css_set, list); | |
| 2500 | - cg->subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id]; | |
| 2501 | - l = l->next; | |
| 2502 | - } while (l != &init_css_set.list); | |
| 2503 | - write_unlock(&css_set_lock); | |
| 2492 | + * newly registered, all tasks and hence the | |
| 2493 | + * init_css_set is in the subsystem's top cgroup. */ | |
| 2494 | + init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id]; | |
| 2504 | 2495 | |
| 2505 | - /* If this subsystem requested that it be notified with fork | |
| 2506 | - * events, we should send it one now for every process in the | |
| 2507 | - * system */ | |
| 2508 | - if (ss->fork) { | |
| 2509 | - struct task_struct *g, *p; | |
| 2510 | - | |
| 2511 | - read_lock(&tasklist_lock); | |
| 2512 | - do_each_thread(g, p) { | |
| 2513 | - ss->fork(ss, p); | |
| 2514 | - } while_each_thread(g, p); | |
| 2515 | - read_unlock(&tasklist_lock); | |
| 2516 | - } | |
| 2517 | - | |
| 2518 | 2496 | need_forkexit_callback |= ss->fork || ss->exit; |
| 2497 | + | |
| 2498 | + /* At system boot, before all subsystems have been | |
| 2499 | + * registered, no tasks have been forked, so we don't | |
| 2500 | + * need to invoke fork callbacks here. */ | |
| 2501 | + BUG_ON(!list_empty(&init_task.tasks)); | |
| 2519 | 2502 | |
| 2520 | 2503 | ss->active = 1; |
| 2521 | 2504 | } |