Messages in this thread | | | Date | Wed, 21 Jan 2009 02:41:56 -0800 | Subject | Re: [PATCH] cpuset: fix allocating page cache/slab object on the unallowed node when memory spread is set | From | Paul Menage <> |
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On Wed, Jan 21, 2009 at 12:06 AM, Miao Xie <miaox@cn.fujitsu.com> wrote: > The task still allocated the page caches on old node after modifying its > cpuset's mems when 'memory_spread_page' was set, it is caused by the old > mem_allowed_list of the task, the current kernel doesn't updates it unless some > function invokes cpuset_update_task_memory_state(), it is too late sometimes.
Can you give a more concrete example of how the current code can break?
> We must update the mem_allowed_list of the tasks in time.
This is a fairly fundamental change to the way that mems_allowed is handled - it dates back to fairly early in cpusets' history.
> - * The task_struct fields mems_allowed and mems_generation may only > - * be accessed in the context of that task, so require no locks. > + * The task_struct fields mems_allowed may only be accessed in the context > + * of that task, so require no locks.
This comment is no longer true, since mems_allowed is now being updated by other processes.
What's to stop a task reading current->mems_allowed and racing with an update from update_tasks_nodemask() ? Or else, why can that not lead to badness?
Paul
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