Date: Tue, 28 Mar 2006 15:38:18 -0500 From: John Baldwin <jhb@freebsd.org> To: Daniel Eischen <deischen@freebsd.org> Cc: Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?= <des@des.no>, src-committers@freebsd.org, cvs-all@freebsd.org, cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/i386/include atomic.h Message-ID: <200603281538.21743.jhb@freebsd.org> In-Reply-To: <200603281528.41502.jhb@freebsd.org> References: <Pine.GSO.4.43.0603281500400.18701-100000@sea.ntplx.net> <200603281528.41502.jhb@freebsd.org>
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On Tuesday 28 March 2006 15:28, John Baldwin wrote: > On Tuesday 28 March 2006 15:04, Daniel Eischen wrote: > > On Tue, 28 Mar 2006, Dag-Erling [iso-8859-1] Sm=F8rgrav wrote: > >=20 > > > John Baldwin <jhb@freebsd.org> writes: > > > > s/off/on/ I trust > > > > > > > > Not true. The tinderbox would attest to that. Please see code suc= h as > > > > this: [...] > > > > > > which uses uintptr_t, not actual pointers, to avoid warnings. In > > > effect, that code is broken. > > > > > > Apply the attached patch, see how far a buildkernel gets... > > > > > > I think the proper thing to do, to cover all your bases, would be to > > > define a MD atomic_*_intptr family which operated on uintptr_t, and > > > define an MI atomic_*_ptr family which operates on void * based on > > > that. > >=20 > > I would like to see that. > >=20 > > > > Even userland uses casts when it uses void * rather than uintptr_t = for > > > > the underlying type. See src/lib/libpthread/sys/lock.c or > > > > src/lib/libthr/thr_umtx.h. > >=20 > > I didn't like having to do that in libpthread. It was confusing > > to me. I'd be happy if I never had to deal with uintptr_t. >=20 > Then please provide the C idiom for declaring a pointer to a volatile > void pointer. volatile void ** declares a pointer to a pointer to a > volatile void. This is a real issue that was causing problems with > refcounting on mbuf's on sparc64 last year due to us not properly > letting the compiler know what values were being invalidated. >=20 > cdecl doesn't seem up to the task. And again, we already had this > discussion N months ago. Actually, my cdecl skills are in decline. :( declare foo as pointer to volatile pointer to void void * volatile *foo The different placement of volatile broken sparc64 though. However, an MI wrapper would work around that issue. I can pursue a patch that adds the wrapper unless one of you two wants to do it. I really wish you'd have spoken up earlier though. This was changed back in July. =2D-=20 John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" =3D http://www.FreeBSD.org
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