Date: Mon, 12 Mar 2007 21:03:45 +0100 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: John Baldwin <jhb@freebsd.org> Cc: Attilio Rao <attilio@freebsd.org>, cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/share/man/man9 Makefile condvar.9 lock.9 mi_switch.9 mtx_pool.9 mutex.9 rwlock.9 sleep.9 sleepqueue.9 sx.9 thread_exit.9 src/sys/kern kern_synch.c src/sys/sys mutex.h rwlock.h sleepqueue.h sx.h systm.h Message-ID: <20070312200345.GB5688@garage.freebsd.pl> In-Reply-To: <200703121535.22140.jhb@freebsd.org> References: <200703092241.l29Mf2Ds062856@repoman.freebsd.org> <200703121116.24667.jhb@freebsd.org> <20070312185638.GA5688@garage.freebsd.pl> <200703121535.22140.jhb@freebsd.org>
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On Mon, Mar 12, 2007 at 03:35:21PM -0400, John Baldwin wrote:
> On Monday 12 March 2007 14:56, Pawel Jakub Dawidek wrote:
> > On Mon, Mar 12, 2007 at 11:16:23AM -0400, John Baldwin wrote:
> > > On Saturday 10 March 2007 15:52, Pawel Jakub Dawidek wrote:
> > > > What about something like this:
> > > >=20
> > > > #define cv_wait(cv, lock) do {
> > > > switch (LO_CLASSINDEX((struct lock_object *)(lock))) {
> > >=20
> > > The problem with a cast is you use type checking. Might as well do t=
his:
> > >=20
> > > #define cv_wait(cv, lock) _cv_wait((cv), (struct lock_object *)(lock))
> >=20
> > This will skip type checking and my version only cast to provide type
> > checking, so when you pass some random variable it will give you an
> > error.
>=20
> Not really, you may pass some garbage and the LO_CLASSINDEX turns out to =
be a=20
> mutex. :) You only get a runtime error, not a compile-time one. =20
> Type-checking by the compiler is nice because you get compile-time errors.
I'll get compile-time error, because cv_wait_mtx() takes
'struct condvar *' and 'struct mtx *' as arguments. So even if some
garbage returns 1, which turns out to be a mutex, call to cv_wait_mtx()
will generate compile-time error.
But it seems the solution may not be that good if it is not very obvious
on a first look. If typeof() thing works, its fine by me, just give me
condvar(9) that works with sx(9) locks:)
--=20
Pawel Jakub Dawidek http://www.wheel.pl
pjd@FreeBSD.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
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