Messages in this thread Patch in this message | | | Date | Tue, 23 Jun 2009 16:10:19 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [PATCH 2/2] memcg: wakeup rmdir waiter if necessary |
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From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
mem_cgroup's pre_destroy() handler tries to reduce its resource usage to 0. But in some case, a charge comes after pre_destroy and rmdir() never finishes because the caller of rmdir() sleeps.
This patch wakes up the caller of rmdir() and let it call pre_destroy(), again.
Note: Making pre_destroy() synchrounous is a way, but it will require some synchronization...as global lock. A method this patch uses is "do asynchronous and check if necessary". Maybe this works better than global synchronization if properly commented.
Reported-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- include/linux/cgroup.h | 7 +++++++ kernel/cgroup.c | 5 ++--- mm/memcontrol.c | 17 +++++++++++++++++ 3 files changed, 26 insertions(+), 3 deletions(-)
Index: fix-rmdir-cgroup/include/linux/cgroup.h =================================================================== --- fix-rmdir-cgroup.orig/include/linux/cgroup.h +++ fix-rmdir-cgroup/include/linux/cgroup.h @@ -365,6 +365,13 @@ int cgroup_task_count(const struct cgrou /* Return true if cgrp is a descendant of the task's cgroup */ int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task); +void __cgroup_wakeup_rmdir_waiters(void); +static inline void cgroup_wakeup_rmdir_waiters(const struct cgroup *cgrp) +{ + if (unlikely(test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))) + __cgroup_wakeup_rmdir_waiters(); +} + /* * Control Group subsystem type. * See Documentation/cgroups/cgroups.txt for details Index: fix-rmdir-cgroup/kernel/cgroup.c =================================================================== --- fix-rmdir-cgroup.orig/kernel/cgroup.c +++ fix-rmdir-cgroup/kernel/cgroup.c @@ -755,10 +755,9 @@ static void cgroup_d_remove_dir(struct d */ DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq); -static void cgroup_wakeup_rmdir_waiters(const struct cgroup *cgrp) +void __cgroup_wakeup_rmdir_waiters(void) { - if (unlikely(test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))) - wake_up_all(&cgroup_rmdir_waitq); + wake_up_all(&cgroup_rmdir_waitq); } static int rebind_subsystems(struct cgroupfs_root *root, Index: fix-rmdir-cgroup/mm/memcontrol.c =================================================================== --- fix-rmdir-cgroup.orig/mm/memcontrol.c +++ fix-rmdir-cgroup/mm/memcontrol.c @@ -1428,6 +1428,7 @@ __mem_cgroup_commit_charge_swapin(struct return; if (!ptr) return; + css_get(&ptr->css); pc = lookup_page_cgroup(page); mem_cgroup_lru_del_before_commit_swapcache(page); __mem_cgroup_commit_charge(ptr, pc, ctype); @@ -1457,6 +1458,13 @@ __mem_cgroup_commit_charge_swapin(struct } rcu_read_unlock(); } + /* + * At swapin, we may charge against cgroup which has no tasks. Such + * cgroups can be removed by rmdir(). If we do charge after + * pre_destroy(), we should call pre_destroy(), again. + */ + cgroup_wakeup_rmdir_waiters(ptr->css.cgroup); + css_put(&ptr->css); } void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) @@ -1663,6 +1671,7 @@ void mem_cgroup_end_migration(struct mem if (!mem) return; + css_get(&mem->css); /* at migration success, oldpage->mapping is NULL. */ if (oldpage->mapping) { target = oldpage; @@ -1702,6 +1711,14 @@ void mem_cgroup_end_migration(struct mem */ if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED) mem_cgroup_uncharge_page(target); + + /* + * At migration, we may charge against cgroup which has no tasks. Such + * cgroups can be removed by rmdir(). If we do charge after + * pre_destroy(), we should call pre_destroy(), again. + */ + cgroup_wakeup_rmdir_waiters(mem->css.cgroup); + css_put(&mem->css); } /*
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