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Date: Wed, 2 Apr 2008 09:31:57 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Balbir Singh <balbir@...ux.vnet.ibm.com> Cc: Paul Menage <menage@...gle.com>, Pavel Emelianov <xemul@...nvz.org>, Hugh Dickins <hugh@...itas.com>, Sudhir Kumar <skumar@...ux.vnet.ibm.com>, YAMAMOTO Takashi <yamamoto@...inux.co.jp>, lizf@...fujitsu.com, linux-kernel@...r.kernel.org, taka@...inux.co.jp, linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [RFC][-mm] Add an owner to the mm_struct (v4) On Tue, 01 Apr 2008 18:13:12 +0530 Balbir Singh <balbir@...ux.vnet.ibm.com> wrote: > + /* > + * Search in the children > + */ > + list_for_each_entry(c, &p->children, sibling) { > + if (c->mm == mm) > + goto assign_new_owner; > + } > + This finds new owner when "current" is multi-threaded and "current" called pthread_create(), right ? > + /* > + * Search in the siblings > + */ > + list_for_each_entry(c, &p->parent->children, sibling) { > + if (c->mm == mm) > + goto assign_new_owner; > + } > + This finds new owner when "current" is multi-threaded and "current" is just a child (means it doesn't call pthread_create()) ? > + /* > + * Search through everything else. We should not get > + * here often > + */ > + do_each_thread(g, c) { > + if (c->mm == mm) > + goto assign_new_owner; > + } while_each_thread(g, c); Doing above in synchronized manner seems too heavy. When this happen ? or Can this be done in lazy "on-demand" manner ? +assign_new_owner: + rcu_read_unlock(); + BUG_ON(c == p); + task_lock(c); + if (c->mm != mm) { + task_unlock(c); + goto retry; + } + cgroup_mm_owner_callbacks(mm->owner, c); + mm->owner = c; + task_unlock(c); +} Why rcu_read_unlock() before changing owner ? Is it safe ? Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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