Date: Wed, 6 Jun 2018 17:06:42 +0200 From: Mateusz Guzik <mjguzik@gmail.com> To: Hans Petter Selasky <hselasky@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r334712 - head/sys/compat/linuxkpi/common/include/asm Message-ID: <CAGudoHFHZk_9qB016bUhcQH4sGCbNLj28FkdJ0Q4M2joR0x3xw@mail.gmail.com> In-Reply-To: <201806061359.w56DxpSZ020224@repo.freebsd.org> References: <201806061359.w56DxpSZ020224@repo.freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, Jun 6, 2018 at 3:59 PM, Hans Petter Selasky <hselasky@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 <johalun0@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>
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAGudoHFHZk_9qB016bUhcQH4sGCbNLj28FkdJ0Q4M2joR0x3xw>