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    SubjectRe: [PATCH] futex: cmpxchg_futex_value_locked API change
    On Wed, 9 Mar 2011 03:25:50 -0800
    Michel Lespinasse <walken@google.com> wrote:

    > On Tue, Mar 08, 2011 at 09:17:11PM +0100, Thomas Gleixner wrote:
    > > On Sun, 6 Mar 2011, Michel Lespinasse wrote:
    > > > The cmpxchg_futex_value_locked API was funny in that it returned either
    > > > the original, user-exposed futex value OR an error code such as -EFAULT.
    > > > This was confusing at best, and could be a source of livelocks in places
    > > > that retry the cmpxchg_futex_value_locked after trying to fix the issue
    > > > by running fault_in_user_writeable().
    > > >
    > > > This change makes the cmpxchg_futex_value_locked API more similar to the
    > > > get_futex_value_locked one, returning an error code and updating the
    > > > original value through a reference argument.
    > >
    > > Ack.
    > >
    > > > static inline int
    > > > -futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
    > > > +futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr,
    > > > + int oldval, int newval)
    > >
    > > Can we please change the arguments to u32 while at it? The futex core
    > > code uses u32 all over the place so those inlines should do the same.
    >
    > All right. Attaching updated version of the diff. I also fixed the s390
    > issue reported by Martin Schwidefsky.

    The inline assmeblies look good now but I get this compile error on s390:

    CC arch/s390/lib/uaccess_pt.o
    arch/s390/lib/uaccess_pt.c:373: error: conflicting types for 'futex_atomic_cmpxchg_pt'
    arch/s390/lib/uaccess.h:21: note: previous declaration of 'futex_atomic_cmpxchg_pt' was here
    arch/s390/lib/uaccess_pt.c:403: warning: initialization from incompatible pointer type
    make[1]: *** [arch/s390/lib/uaccess_pt.o] Error 1

    The trouble is this part of the patch:

    -int futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval)
    +int futex_atomic_cmpxchg_pt(int *uval, int __user *uaddr,
    + int oldval, int newval)

    You need to change these "int"s to "u32"s.

    --
    blue skies,
    Martin.

    "Reality continues to ruin my life." - Calvin.



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