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    SubjectRe: device driver / char module interrupt vector -> user space code
    On Fri, Aug 09, 2002 at 11:34:00AM +0100, Alan Cox wrote:
    > On Fri, 2002-08-09 at 09:49, SA wrote:
    > > I am writing a char module for a PCI stage controller and want to add the
    > > following functionality;
    > >
    > > The device will generate an interrupt (or software trigger) and I want this to
    > > run a bit of user code with relatively latency. (<1ms). I am unclear how to
    > > do this while still separating the user from the kernel code and maintaining
    > > security - would this usually be handled by issuing a signal to the user space
    > > process? if so how and what latency can I expect?
    > You could deliver a signal, or if appropriate you can have a system call
    > that blocks until the IRQ. To get good reliable latency, mlockall() the
    > process you need to be real time, and set it to a real time scheduling
    > priority.

    If you noticed the discussion about signal delivery and context switch
    latency, a syscall (can be ioctl on special device) waiting for the
    event would be faster than signal.

    Jan 'Bulb' Hudec <>
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