Messages in this thread | | | Date | Tue, 30 Jun 2009 18:23:04 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 2/2] cgroup: exlclude release rmdir |
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On Tue, 30 Jun 2009 02:15:03 -0700 Paul Menage <menage@google.com> wrote:
> On Tue, Jun 30, 2009 at 2:03 AM, KAMEZAWA > Hiroyuki<kamezawa.hiroyu@jp.fujitsu.com> wrote: > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > > > Paul Menage pointed out that css_get()/put() only for avoiding race with > > rmdir() is complicated and these should be treated as it is for. > > > > This adds > > - cgroup_exclude_rmdir() ....prevent rmdir() for a while. > > - cgroup_release_rmdir() ....rerun rmdir() if necessary. > > And hides cgroup_wakeup_rmdir_waiter() into kernel/cgroup.c, again. > > Wouldn't it be better to merge these into a single patch? Having one > patch that exposes complexity only to take it away in the following > patch seems unnecessary; the combined patch would be simpler than the > constituents. > This patch is _not_ tested by Nishimura. What I want is patch 1/2, it's BUGFIX and passed tests by him. I trust his test very much. I want the patch 1/2 should be on fast-path as BUGFIX.
But, I think this patch 2/2 is not for fast-path. This is something new but just a refactoring.
Anyway, I can postpone this until things are settled. Only merging patch 1/2 is okay for me now.
Thanks, -Kame
> Paul > > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > > > --- > > include/linux/cgroup.h | 21 +++++++++++---------- > > kernel/cgroup.c | 17 +++++++++++++++-- > > mm/memcontrol.c | 12 ++++-------- > > 3 files changed, 30 insertions(+), 20 deletions(-) > > > > Index: mmotm-2.6.31-Jun25/include/linux/cgroup.h > > =================================================================== > > --- mmotm-2.6.31-Jun25.orig/include/linux/cgroup.h > > +++ mmotm-2.6.31-Jun25/include/linux/cgroup.h > > @@ -366,17 +366,18 @@ int cgroup_task_count(const struct cgrou > > int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task); > > > > /* > > - * Allow to use CGRP_WAIT_ON_RMDIR flag to check race with rmdir() for subsys. > > - * Subsys can call this function if it's necessary to call pre_destroy() again > > - * because it adds not-temporary refs to css after or while pre_destroy(). > > - * The caller of this function should use css_tryget(), too. > > + * When the subsys has to access css and may add permanent refcnt to css, > > + * it should take care of racy conditions with rmdir(). Following set of > > + * functions, is for stop/restart rmdir if necessary. > > + * Because these will call css_get/put, "css" should be alive css. > > + * > > + * cgroup_exclude_rmdir(); > > + * ...do some jobs which may access arbitrary empty cgroup > > + * cgroup_release_rmdir(); > > */ > > -void __cgroup_wakeup_rmdir_waiters(void); > > -static inline void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp) > > -{ > > - if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))) > > - __cgroup_wakeup_rmdir_waiters(); > > -} > > + > > +void cgroup_exclude_rmdir(struct cgroup_subsys_state *css); > > +void cgroup_release_rmdir(struct cgroup_subsys_state *css); > > > > /* > > * Control Group subsystem type. > > Index: mmotm-2.6.31-Jun25/kernel/cgroup.c > > =================================================================== > > --- mmotm-2.6.31-Jun25.orig/kernel/cgroup.c > > +++ mmotm-2.6.31-Jun25/kernel/cgroup.c > > @@ -738,11 +738,24 @@ static void cgroup_d_remove_dir(struct d > > */ > > DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq); > > > > -void __cgroup_wakeup_rmdir_waiters(void) > > +static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp) > > { > > - wake_up_all(&cgroup_rmdir_waitq); > > + if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))) > > + wake_up_all(&cgroup_rmdir_waitq); > > } > > > > +void cgroup_exclude_rmdir(struct cgroup_subsys_state *css) > > +{ > > + css_get(css); > > +} > > + > > +void cgroup_release_rmdir(struct cgroup_subsys_state *css) > > +{ > > + cgroup_wakeup_rmdir_waiter(css->cgroup); > > + css_put(css); > > +} > > + > > + > > static int rebind_subsystems(struct cgroupfs_root *root, > > unsigned long final_bits) > > { > > Index: mmotm-2.6.31-Jun25/mm/memcontrol.c > > =================================================================== > > --- mmotm-2.6.31-Jun25.orig/mm/memcontrol.c > > +++ mmotm-2.6.31-Jun25/mm/memcontrol.c > > @@ -1461,7 +1461,7 @@ __mem_cgroup_commit_charge_swapin(struct > > return; > > if (!ptr) > > return; > > - css_get(&ptr->css); > > + 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); > > @@ -1496,9 +1496,7 @@ __mem_cgroup_commit_charge_swapin(struct > > * 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_wakeup_rmdir_waiter(ptr->css.cgroup); > > - css_put(&ptr->css); > > - > > + cgroup_release_rmdir(&ptr->css); > > } > > > > void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) > > @@ -1704,7 +1702,7 @@ void mem_cgroup_end_migration(struct mem > > > > if (!mem) > > return; > > - css_get(&mem->css); > > + cgroup_exclude_rmdir(&mem->css); > > /* at migration success, oldpage->mapping is NULL. */ > > if (oldpage->mapping) { > > target = oldpage; > > @@ -1749,9 +1747,7 @@ void mem_cgroup_end_migration(struct mem > > * 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_wakeup_rmdir_waiter(mem->css.cgroup); > > - css_put(&mem->css); > > - > > + cgroup_release_rmdir(&mem->css); > > } > > > > /* > > > > >
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