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    SubjectRe: programming for preemption (was: [PATCH] 2.5.46: access permission filesystem)
    Date
    Andrew Morton <akpm@digeo.com> writes:

    > Olaf Dietsche wrote:
    >>
    >> Ben Clifford <benc@hawaga.org.uk> writes:
    >>
    >> > I still get those stack traces, though...
    >>
    >> I retested with CONFIG_PREEMPT=y and now I get those stack traces,
    >> too. So, it seems my code is not preempt safe.
    >>
    >
    > It's not that your code is unsafe with preemption. It's just that
    > CONFIG_PREEMPT=y turns on the debugging infrastructure which allows
    > us to detect things like calling kmalloc(GFP_KERNEL) inside spinlock.

    Thanks for this hint. So this means kmalloc(GFP_KERNEL) inside
    spinlock is not necessarily dangerous, but should be avoided if
    possible? Is using a semaphore better than using spinlocks? Is
    there a list of dos and don'ts for preempt kernels beside
    Documentation/preempt-locking.txt?

    And btw, who is "us"?

    Regards, Olaf.
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