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    SubjectRe: GGI and cli/sti in X
    On Mar 29, Pavel Machek wrote:

    > > > I get 5 or 6 ughs everytime somone runs X onmy system so I'd say your
    > > > correct, the ughs are allways in do_page_fault. The ughs are normal on
    > > > any system I've seen with < 16 megs ram. The every once and a while
    > >
    > > The "Ugh" is logging the fact someone attempted to handle a page fault while
    > > having interrupts disabled. This is an extremely bad thing. There are two causes
    > >
    > > 1. Incorrect kernel code (I think most of these are now dead)
    > > 2. Some user process as root which has the misguided idea it can disable
    > > interrupts after using the iopl() syscall. Well it can't. Not unless
    > > its prepaged everything it needs and mlock()'d those pages
    >
    > XF86 3.1.2 (latest I have convient access to) does *not* do *any*
    > cli()/sti()'s. At least in os-dependend section disable_interrupts()
    > is empty function.
    >
    > > so its either a kernel or an X bug.
    >
    > ...so I doubt this is X bug. It would be nice if some X hacker joined
    > this debate...

    more recent XFree86 sources have non-empty xf86DisableInterrupts()
    (don't know when this has changed). but if you check XFree86 sources
    for S3 and S3/SVGA (that's what I'm falmilar with;) you'll find
    that interrupts are _only_ disabled for ICD2061A clock setting (in s3_init_clock())
    and for probing clock values for non-programmable clocks (in xf86GetClocks(),
    and the latter you can avoid at runtime by specifying clock values in config file;
    and ICD2061A clockchips aren't used anymore). using

    disas xf86GetClocks
    disas s3_init_clock

    in gdb will show that both routines lay pretty well in one page (if they don't,
    we'd get many reports for sure;). while this isn't perfect, it can be improved
    using mlock() for that routines and it's for sure not something which can _only_
    be done using GGI.



    Harald
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