Messages in this thread | | | Subject | Re: [PATCH -mmotm 1/5] memcg: disable irq at page cgroup lock | From | Peter Zijlstra <> | Date | Fri, 23 Apr 2010 22:54:34 +0200 |
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On Fri, 2010-04-23 at 13:17 -0700, Greg Thelen wrote: > - lock_page_cgroup(pc); > + /* > + * Unless a page's cgroup reassignment is possible, then avoid grabbing > + * the lock used to protect the cgroup assignment. > + */ > + rcu_read_lock();
Where is the matching barrier?
> + smp_rmb(); > + if (unlikely(mem_cgroup_account_move_ongoing)) { > + local_irq_save(flags);
So the added irq-disable is a bug-fix?
> + lock_page_cgroup(pc); > + locked = true; > + } > + > mem = pc->mem_cgroup; > if (!mem || !PageCgroupUsed(pc)) > goto done; > @@ -1449,6 +1468,7 @@ void mem_cgroup_update_file_mapped(struct page *page, int val) > /* > * Preemption is already disabled. We can use __this_cpu_xxx > */ > + VM_BUG_ON(preemptible());
Insta-bug here, there is nothing guaranteeing we're not preemptible here.
> if (val > 0) { > __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]); > SetPageCgroupFileMapped(pc); > @@ -1458,7 +1478,11 @@ void mem_cgroup_update_file_mapped(struct page *page, int val) > } > > done: > - unlock_page_cgroup(pc); > + if (unlikely(locked)) { > + unlock_page_cgroup(pc); > + local_irq_restore(flags); > + } > + rcu_read_unlock(); > }
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