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    SubjectRe: kmalloc without GFP_xxx?
    On Wed, 2005-06-29 at 09:44 -0400, Steven Rostedt wrote:
    > 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.

    There are cases where using spin_lock instead of _irqsave version is a
    matter of correctness. For example, the page table lock beeing always
    taking without _irq is important to let the IPIs flow.


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      Last update: 2005-06-30 03:14    [W:0.028 / U:15.220 seconds]
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