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    SubjectRe: Can current macro be accessed from interrupt context?
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    On Thu, Oct 22, 2009 at 4:27 AM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
    > On Thu, Oct 22, 2009 at 04:10:49AM -0700, Leonidas . wrote:
    >> Hello,
    >>
    >> Going through UTLK, it says that current macro makes sense only in
    >> case of process context,
    >> in case of interrupt context it is invalid.
    >
    >
    > Indeed, usually it makes only sense in process context.
    >
    >
    >> But current would still be pointing to interrupted process right? The
    >> pointer would still be valid?
    >
    >
    >
    > Yeah, unless you irq handler executes in a threaded interrupt, in
    > which case current will be pointing to the given irq thread.

    Threaded interrupt handlers? I am sorry, I am new to kernel development
    and not fully aware of the intricacies. Do you mean bottom half handlers here?

    > There are few tiny cases where it is unsafe to deref "current",
    > such as the very beginning of a cpu's awakening, when the per cpu
    > datas are not yet ready for this cpu.
    >

    Okay, I guess, in my case this would not be a problem then since this is about
    early init.

    >> Can I safely assume that whether or not interrupt handlers are
    >> executing on separate stacks or
    >> interrupted threads stack, current macro can be accessed from interrupt context?
    >
    >
    > Yep.
    > For example we do that in the function graph tracer. Because we store return
    > addresses of functions in the "current" task structure. Even if the task
    > is interrupted, it still makes sense to use current because we want
    > to know the flow of execution as a linear thing per cpu, the interrupt
    > is part of that flow
    >
    > I hope that helps.
    >

    Can you give pointers to the source code of this project?

    > Frederic.
    >
    >


    -Leo.


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