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    SubjectRe: kmalloc without GFP_xxx?


    On Wed, 29 Jun 2005, Arjan van de Ven wrote:
    > >
    > > but it sets irqs_disabled() IIRC.
    >
    > only spin_lock_irq() and co do.
    > not the simple spin_lock()
    >

    It may be dangerous to use spin_lock with interrupts enabled, since you
    have to make sure that no interrupt ever grabs that lock. Although I do
    recall seeing a few locks like this. But even so, you can transfer the
    latency of the interrupts going off while holding that lock to another CPU
    which IMHO is a bad thing. Also a simple spin_lock would disable
    preemption with CONFIG_PREEMPT set and that would make in_atomic fail.
    But to implement a kmalloc_auto you would always need to have a preempt
    count.

    I'm not for a kmalloc_auto, but something like it would be useful for a
    function that can work for either context, and just fail nicely if the
    ATOMIC is set and the malloc can't get memory. A function like this would
    currently have to always use ATOMIC even if it could have used KERNEL for
    some scenarios, since it would suffer the same pitfalls as a kmalloc_auto
    in determining its context.

    -- Steve

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