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    SubjectRe: kill -9 <pid of X>
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    > > The bigger problems are that X11 is subject to being killed with sig 9
    > > (which with a horrible kernel hack can be blocked for iopl3 processes)
    >
    > Is that so horrible? If X is going to bang hardware like kernel code,
    > it may as well act like kernel code.

    kernel code doesnt get pre-empted without warning, killed due to
    lack of memory and other stuff. Its a more controlled space.

    > > not that big a deal - a setuid "sak signal" ioctl akin to the way you
    > > take over console switching covers it.
    >
    > Yes, as long as X won't let a user remap SAK.

    X shouldnt be capable of remapping SAK

    > > I'd agree however - you don't need to put all mode switching code in
    > > kernel if you allow iopl3 proceses to lock out sig 9 and you provide
    > > a sak hook. Oom should be solvable its just harder
    >
    > Oom is easy: mlockall()

    Bad luck X11 is designed to make good use of the paging. mlockall does
    work for Linus suggested mode changing daemon

    > If X is going to play with hardware, then mlockall() is simply the
    > correct solution. X already disables interrupts sometimes. X can use
    > DMA too then, though a system call to get physical addresses would help.

    You can't DMA to user space. To do that right is hard. Linus turned down
    a couple of "almost right" patches for 2.1.x so until 2.3.x if you want
    DMA you gotta be in the kernel.

    Alan


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