On Wed, Jun 6, 2018 at 3:59 PM, Hans Petter Selasky <hsela...@freebsd.org> wrote:
> Author: hselasky > Date: Wed Jun 6 13:59:51 2018 > New Revision: 334712 > URL: https://svnweb.freebsd.org/changeset/base/334712 > > Log: > Implement the atomic_dec_if_positive() function in the LinuxKPI. > > Submitted by: Johannes Lundberg <johal...@gmail.com> > MFC after: 1 week > Sponsored by: Mellanox Technologies > Sponsored by: Limelight Networks > > Modified: > head/sys/compat/linuxkpi/common/include/asm/atomic.h > > Modified: head/sys/compat/linuxkpi/common/include/asm/atomic.h > ============================================================ > ================== > --- head/sys/compat/linuxkpi/common/include/asm/atomic.h Wed Jun > 6 13:37:31 2018 (r334711) > +++ head/sys/compat/linuxkpi/common/include/asm/atomic.h Wed Jun > 6 13:59:51 2018 (r334712) > @@ -235,6 +235,22 @@ atomic_cmpxchg(atomic_t *v, int old, int new) > __ret.val; \ > }) > > +static inline int > +atomic_dec_if_positive(atomic_t *v) > +{ > + int retval; > + int curr; > + > + do { > + curr = atomic_read(v); > + retval = curr - 1; > + if (unlikely(retval < 0)) > + break; > + } while (!likely(atomic_cmpset_int(&v->counter, curr, retval))); > + > + return (retval); > +} > + > cmpset loops are crap since they require an explicit re-read of the target value see fcmpset and refcount_acquire_if_not_zero for an example use -- Mateusz Guzik <mjguzik gmail.com> _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
