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    SubjectRe: [PATCH -v2 19/33] locking,powerpc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}{,_relaxed,_acquire,_release}()
    On Wed, Jun 01, 2016 at 11:11:38AM +0800, Boqun Feng wrote:
    > Hi Peter,
    >
    > On Tue, May 31, 2016 at 12:19:44PM +0200, Peter Zijlstra wrote:
    > [snip]
    > >
    > > @@ -329,20 +361,53 @@ atomic64_##op##_return_relaxed(long a, a
    > > return t; \
    > > }
    > >
    > > +#define ATOMIC64_FETCH_OP_RELAXED(op, asm_op) \
    > > +static inline long \
    > > +atomic64_fetch_##op##_relaxed(long a, atomic64_t *v) \
    > > +{ \
    > > + long res, t; \
    > > + \
    > > + __asm__ __volatile__( \
    > > +"1: ldarx %0,0,%4 # atomic64_fetch_" #op "_relaxed\n" \
    > > + #asm_op " %1,%3,%0\n" \
    > > +" stdcx. %1,0,%4\n" \
    > > +" bne- 1b\n" \
    > > + : "=&r" (res), "=&r" (t), "+m" (v->counter) \
    > > + : "r" (a), "r" (&v->counter) \
    > > + : "cc"); \
    > > + \
    > > + return t; \
    >
    > Looks like I missed this one in v1, it should be
    >
    > return res;
    >
    > because the primitives will return the values before modified by the
    > operations.
    >

    FWIW, I tested on ppc with ATOMIC64_SELFTEST=y for the following branch:

    git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/atomic (afee54ef5b1f2b04)

    without this modification, I can hit:

    ------------[ cut here ]------------
    kernel BUG at lib/atomic64_test.c:181!
    Oops: Exception in kernel mode, sig: 5 [#1]

    with this modification, all the atomic selftests are passed ;-)

    Regards,
    Boqun
    [unhandled content-type:application/pgp-signature]
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