Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-11-10 22:21:40 +00:00
Code Issues Packages Projects Releases Wiki Activity

memcg: remove memcg_tasklist

Browse Source 
memcg_tasklist was introduced at commit 7f4d454d(memcg: avoid deadlock
caused by race between oom and cpuset_attach) instead of cgroup_mutex to
fix a deadlock problem.  The cgroup_mutex, which was removed by the
commit, in mem_cgroup_out_of_memory() was originally introduced at commit
c7ba5c9e (Memory controller: OOM handling).

IIUC, the intention of this cgroup_mutex was to prevent task move during
select_bad_process() so that situations like below can be avoided.

  Assume cgroup "foo" has exceeded its limit and is about to trigger oom.
  1. Process A, which has been in cgroup "baa" and uses large memory, is just
     moved to cgroup "foo". Process A can be the candidates for being killed.
  2. Process B, which has been in cgroup "foo" and uses large memory, is just
     moved from cgroup "foo". Process B can be excluded from the candidates for
     being killed.

But these race window exists anyway even if we hold a lock, because
__mem_cgroup_try_charge() decides wether it should trigger oom or not
outside of the lock.  So the original cgroup_mutex in
mem_cgroup_out_of_memory and thus current memcg_tasklist has no use.  And
IMHO, those races are not so critical for users.

This patch removes it and make codes simpler.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: 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>
This commit is contained in:
Daisuke Nishimura 2009-12-15 16:47:13 -08:00 committed by Linus Torvalds
parent d31f56dbf8
commit 9ab322caa3
1 changed files with 0 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
mm/memcontrol.c
View File

@ -55,7 +55,6 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
#define do_swap_account (0) #define do_swap_account (0)
#endif #endif
static DEFINE_MUTEX(memcg_tasklist); /* can be hold under cgroup_mutex */
#define SOFTLIMIT_EVENTS_THRESH (1000) #define SOFTLIMIT_EVENTS_THRESH (1000)
/* /*
@ -1481,9 +1480,7 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
if (!nr_retries--) { if (!nr_retries--) {
if (oom) { if (oom) {
mutex_lock(&memcg_tasklist);
mem_cgroup_out_of_memory(mem_over_limit, gfp_mask); mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
mutex_unlock(&memcg_tasklist);
record_last_oom(mem_over_limit); record_last_oom(mem_over_limit);
} }
goto nomem; goto nomem;
@ -3393,12 +3390,10 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss,
struct task_struct *p, struct task_struct *p,
bool threadgroup) bool threadgroup)
{ {
mutex_lock(&memcg_tasklist);
/* /*
* FIXME: It's better to move charges of this process from old * FIXME: It's better to move charges of this process from old
* memcg to new memcg. But it's just on TODO-List now. * memcg to new memcg. But it's just on TODO-List now.
*/ */
mutex_unlock(&memcg_tasklist);
} }
struct cgroup_subsys mem_cgroup_subsys = { struct cgroup_subsys mem_cgroup_subsys = {