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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