Messages in this thread | | | Date | Wed, 2 Apr 2008 09:31:57 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [RFC][-mm] Add an owner to the mm_struct (v4) |
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On Tue, 01 Apr 2008 18:13:12 +0530 Balbir Singh <balbir@linux.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
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