Date: Fri, 24 Aug 2007 14:29:52 +0000 From: Kris Kennaway <kris@FreeBSD.org> To: Pawel Jakub Dawidek <pjd@FreeBSD.org> Cc: Attilio Rao <attilio@freebsd.org>, Alfred Perlstein <alfred@freebsd.org>, freebsd-arch@freebsd.org Subject: Re: Lockless uidinfo. Message-ID: <20070824142952.GA24469@hub.freebsd.org> In-Reply-To: <20070824140927.GC14536@garage.freebsd.pl> References: <20070818120056.GA6498@garage.freebsd.pl> <20070818155041.GY90381@elvis.mu.org> <20070818161449.GE6498@garage.freebsd.pl> <200708211403.29293.jhb@freebsd.org> <20070821191902.GA4187@garage.freebsd.pl> <20070821202136.GB4187@garage.freebsd.pl> <3bbf2fe10708221202h44b3258cyf5ca5e9b867ac0e7@mail.gmail.com> <20070824140927.GC14536@garage.freebsd.pl>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, Aug 24, 2007 at 04:09:27PM +0200, Pawel Jakub Dawidek wrote: > On Wed, Aug 22, 2007 at 09:02:53PM +0200, Attilio Rao wrote: > > 2007/8/21, Pawel Jakub Dawidek <pjd@freebsd.org>: > > > > > > New patch is here: > > > > > > http://people.freebsd.org/~pjd/patches/uidinfo_waitfree.patch > > > > --- sys/ia64/include/atomic.h.orig > > +++ sys/ia64/include/atomic.h > > @@ -370,4 +370,15 @@ > > > > #define atomic_fetchadd_int atomic_fetchadd_32 > > > > +static __inline u_long > > +atomic_fetchadd_long(volatile u_long *p, u_long v) > > +{ > > + u_long value; > > + > > + do { > > + value = *p; > > + } while (!atomic_cmpset_64(p, value, value + v)); > > + return (value); > > +} > > + > > > > In cycles like those, as you get spinning, I would arrange things in > > order to do a cpu_spinwait(). Like this: > > > > for (;;) { > > value = *p; > > if (atomic_cmpset_64(p, value, value + v)) > > break; > > cpu_spinwait(); > > } > > In this case there is no difference as this is MI ia64 code and > cpu_spinwait() is defined as /* nothing */ there. As a general rule, > this might be a good idea. Better to still do it in case that changes. Kris
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20070824142952.GA24469>