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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2009-07-29 15:04:06 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-07-29 19:10:35 -0700
commit887032670d47366a8c8f25396ea7c14b7b2cc620 (patch)
treee5f9ece5ab9239648e8d7051ccb9a217d92553d7 /mm/memcontrol.c
parentf0d83679a8d471dc8b646919f70595d6fe8c9606 (diff)
downloadlinux-887032670d47366a8c8f25396ea7c14b7b2cc620.tar.bz2
cgroup avoid permanent sleep at rmdir
After commit ec64f51545fffbc4cb968f0cea56341a4b07e85a ("cgroup: fix frequent -EBUSY at rmdir"), cgroup's rmdir (especially against memcg) doesn't return -EBUSY by temporary ref counts. That commit expects all refs after pre_destroy() is temporary but...it wasn't. Then, rmdir can wait permanently. This patch tries to fix that and change followings. - set CGRP_WAIT_ON_RMDIR flag before pre_destroy(). - clear CGRP_WAIT_ON_RMDIR flag when the subsys finds racy case. if there are sleeping ones, wakes them up. - rmdir() sleeps only when CGRP_WAIT_ON_RMDIR flag is set. Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Reported-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Reviewed-by: Paul Menage <menage@google.com> Acked-by: Balbir Sigh <balbir@linux.vnet.ibm.com> Signed-off-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>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c23
1 files changed, 20 insertions, 3 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e717964cb5a0..fd4529d86de5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1207,6 +1207,12 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
ret = 0;
out:
unlock_page_cgroup(pc);
+ /*
+ * We charges against "to" which may not have any tasks. Then, "to"
+ * can be under rmdir(). But in current implementation, caller of
+ * this function is just force_empty() and it's garanteed that
+ * "to" is never removed. So, we don't check rmdir status here.
+ */
return ret;
}
@@ -1428,6 +1434,7 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
return;
if (!ptr)
return;
+ cgroup_exclude_rmdir(&ptr->css);
pc = lookup_page_cgroup(page);
mem_cgroup_lru_del_before_commit_swapcache(page);
__mem_cgroup_commit_charge(ptr, pc, ctype);
@@ -1457,8 +1464,12 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
}
rcu_read_unlock();
}
- /* add this page(page_cgroup) to the LRU we want. */
-
+ /*
+ * At swapin, we may charge account against cgroup which has no tasks.
+ * So, rmdir()->pre_destroy() can be called while we do this charge.
+ * In that case, we need to call pre_destroy() again. check it here.
+ */
+ cgroup_release_and_wakeup_rmdir(&ptr->css);
}
void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)
@@ -1664,7 +1675,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
if (!mem)
return;
-
+ cgroup_exclude_rmdir(&mem->css);
/* at migration success, oldpage->mapping is NULL. */
if (oldpage->mapping) {
target = oldpage;
@@ -1704,6 +1715,12 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
*/
if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
mem_cgroup_uncharge_page(target);
+ /*
+ * At migration, we may charge account against cgroup which has no tasks
+ * So, rmdir()->pre_destroy() can be called while we do this charge.
+ * In that case, we need to call pre_destroy() again. check it here.
+ */
+ cgroup_release_and_wakeup_rmdir(&mem->css);
}
/*