Date: Thu, 12 May 2011 19:30:32 +0200 From: Attilio Rao <attilio@freebsd.org> To: Artem Belevich <art@freebsd.org> Cc: svn-src-projects@freebsd.org, Oleksandr Tymoshenko <gonzo@freebsd.org>, src-committers@freebsd.org, Warner Losh <imp@freebsd.org>, Bruce Evans <brde@optusnet.com.au> Subject: Re: svn commit: r221614 - projects/largeSMP/sys/powerpc/include Message-ID: <BANLkTimj3ohmvACmvcPa3yrdsUj=4D2V3Q@mail.gmail.com> In-Reply-To: <BANLkTinaWDcaiZiB3G5Szoaho1jVSeniMA@mail.gmail.com> References: <201105080039.p480doiZ021493@svn.freebsd.org> <BANLkTi=e7GtBM-PTq9yJHSLRoaOWh62AeA@mail.gmail.com> <BANLkTiktwEvRktZrGOqKKB2iSB99a3Jw=g@mail.gmail.com> <BANLkTik17r-XampEdO%2BsQ7aMOL_SDyhG=g@mail.gmail.com> <BANLkTinaWDcaiZiB3G5Szoaho1jVSeniMA@mail.gmail.com>
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2011/5/12 Artem Belevich <art@freebsd.org>: > On Thu, May 12, 2011 at 3:22 PM, Attilio Rao <attilio@freebsd.org> wrote: >> 2011/5/12 Artem Belevich <art@freebsd.org>: >>> On Thu, May 12, 2011 at 5:15 AM, Attilio Rao <attilio@freebsd.org> wrot= e: >>>> 2011/5/8 Attilio Rao <attilio@freebsd.org>: >>>>> Author: attilio >>>>> Date: Sun May =C2=A08 00:39:49 2011 >>>>> New Revision: 221614 >>>>> URL: http://svn.freebsd.org/changeset/base/221614 >>>>> >>>>> Log: >>>>> =C2=A0All architectures define the size-bounded types (uint32_t, uint= 64_t, etc.) >>>>> =C2=A0starting from base C types (int, long, etc). >>>> >>>> mips seems having the same issue, so here is my patch: >>>> http://www.freebsd.org/~attilio/largeSMP/mips-atomic.diff >>> >>> I see at least one problem. N32 ABI is ILP32 even though it can use >>> 64-bit registers for "long long". >> >> I'm sorry but this _longlong is non standard for our atomic scheme, >> nothing in the kernel uses it and in general I'd say to not add them >> if not strictly necessary. >> Said that, in the -CURRENT code it doesn't seem present, or I'm missing = it? > > The key is that N32 ABI does use 64-bit registers and can perform > 64-bit atomic ops. > Unfortunately, 64-bit type is long long or [u]int64_t. The point is > that it's not *long*. >> >>>> #if defined(__mips_n64) || defined(__mips_n32) >>>> static __inline void >>>>-atomic_set_64(__volatile uint64_t *p, uint64_t v) >>>>+atomic_set_long(__volatile u_long *p, u_long v) >>> >>> Using _long here would not match the assembly on N32. >>> >>> If you stick with your changes, then you should drop __mips_n32 from >>> the ifdef above. >>> You may also want to add atomic_*_longlong for n32. Actually, for o64 a= s well. >> >> I'm not entirely sure in which way the above is different... or at >> least, I may have overlooked the _long support for __mips_n32... can >> you please elaborate a bit more? > > The inline assembly for atomic_set_long above uses 64-bit load/store. > This is not going to work for 32-bit long in N32 ABI. That cames from my mips assembly ignorance, I apologize. I just gave a look at types.h and what it just I basically see is: - __mips_n32 is just the same as plain !__mips_n32 && !__mips_n64 - __mips_n64 just addes the operations for 64 bits operands Thus what I need to make sure is: - __mips_n32 (and !__mips_n32 && !__mips_n64) case work on 32 bits operand on long too - __mips_n64 works on 64 bits long operands Do you have a specifi opinion on _char/_short operands? Do you have strong feeling on the _longlong stuff? Do you think it will be useful in mips? About the last question I think that it would be more fair to use _64 directly, when possible. Thanks, Attilio --=20 Peace can only be achieved by understanding - A. Einstein
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