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    SubjectRe: [PATCH 1/2] staging: zram: minimize `slot_free_lock' usage (v2)
    On (09/09/13 17:52), Dan Carpenter wrote:
    > On Mon, Sep 09, 2013 at 05:42:59PM +0300, Sergey Senozhatsky wrote:
    > > > 3) Explain why it is safe to test zram->slot_free_rq when we are not
    > > > holding the lock. I think it is unsafe. I don't want to even think
    > > > about it without the numbers.
    > >
    > > atomic pointer test, which is either NULL or !NULL.
    > >
    >
    > That's not how concurency works. Atomic types are complicated than
    > that. Anyway, the zram maintainers don't need me to explain that to
    > them so I'll let them take over from here.
    >

    yes, I understand that. but can't we check slot_free_rq pointer
    (32 or 64 bit read) w/o locking to just decide if we must:
    -- call handle_pending_slot_free()
    -- take the slot_free_lock
    -- check slot_free_rq again (this time under the slot_free_lock) and perform
    slot_free_rq operations while it is !NULL.

    -ss

    > regards,
    > dan carpenter
    >


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