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    SubjectRe: [PATCH/RFC] m68k/bitops: Make bitmap data pointer of atomic ops volatile
    On Tue, Jun 07, 2011 at 01:22:29PM +0200, Arnd Bergmann wrote:
    > On Tuesday 07 June 2011, Geert Uytterhoeven wrote:
    > > You mean the host_busy variable in the IDE code?
    > > That would also apply to context_flag in the DRM code:
    > >
    > > drivers/gpu/drm/drm_context.c:233: warning: passing argument 2 of
    > > ‘__constant_test_and_set_bit’ discards qualifiers from pointer target
    > > type
    > > drivers/gpu/drm/drm_context.c:233: warning: passing argument 2 of
    > > ‘__generic_test_and_set_bit’ discards qualifiers from pointer target
    > > type
    >
    > Yes, that fits the same category.
    >
    > > > is wrong, though. It probably doesn't hurt to do both.
    > >
    > > asm-generic/bitops/atomic.h has the volatiles everywhere. That's why
    > > I'm wondering.
    >
    > I guess what happened is that some variables are traditionally marked
    > as volatile although they shouldn't be, and most architectures have
    > adapted their bitops to make the warnings go away. If you see more
    > warnings of that kind, it's probably fine to just do the same on m68k.
    > The volatile modifier doesn't really hurt in this case.

    These operations are required to be atomic and therefore they
    must be suitable for use with volatile-qualified variables.

    Ben.

    --
    Ben Hutchings
    We get into the habit of living before acquiring the habit of thinking.
    - Albert Camus
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