Re: zram OOM behavior

[Luigi Semenzato <semenzato@google.com>]

I found the source, and maybe the cause, of the problem I am
experiencing when running out of memory with zram enabled.  It may be
a known problem.  The OOM killer doesn't find any killable process
because select_bad_process() keeps returning -1 here:

    /*
     * This task already has access to memory reserves and is
     * being killed. Don't allow any other task access to the
     * memory reserve.
     *
     * Note: this may have a chance of deadlock if it gets
     * blocked waiting for another task which itself is waiting
     * for memory. Is there a better alternative?
     */
    if (test_tsk_thread_flag(p, TIF_MEMDIE)) {
        if (unlikely(frozen(p)))
            __thaw_task(p);
        if (!force_kill)
            return ERR_PTR(-1UL);
    }

select_bad_process() is called by out_of_memory() in __alloc_page_may_oom().

If this is the problem, I'd love to hear about solutions!

<BEGIN SHAMELESS PLUG>
if we can get this to work, it will help keep the cost of laptops down!
http://www.google.com/intl/en/chrome/devices/
<END SHAMELESS PLUG>

P.S. Chromebooks are sweet things for kernel debugging because they
boot so quickly (5-10s depending on the model).

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