From: Aurelien Jarno <aurelien@aurel32.net>
To: Richard Henderson <rth7680@gmail.com>
Cc: Matt Turner <mattst88@gmail.com>,
Carlos O'Donell <carlos@systemhalted.org>,
debian-alpha@lists.debian.org, debian-glibc@lists.debian.org,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
linux-alpha@vger.kernel.org
Subject: Re: Help on memchr() EGLIBC assembly code
Date: Sun, 19 Jul 2009 16:29:33 +0200 [thread overview]
Message-ID: <20090719142933.GO18682@hall.aurel32.net> (raw)
In-Reply-To: <4A5E3272.4040904@gmail.com>
On Wed, Jul 15, 2009 at 12:48:02PM -0700, Richard Henderson wrote:
> On 07/13/2009 03:16 PM, Matt Turner forwarded:
>>>>> The problem is that the memchr() function on alpha uses prefetch, which
>>>>> can cause a page boundary to be crossed, while the standards (POSIX and
>>>>> C99) says it should stop when a match is found.
>
> That's not supposed to matter -- faults from prefetch are supposed to be
> ignored; see do_page_fault:
The problem is that the "prefech" is not done with $31, but using $1 and
$3. It is called "prefetch" in the code, but it is more like "read a value
in advance".
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
next prev parent reply other threads:[~2009-07-19 14:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20090713173104.GA13883@hall.aurel32.net>
[not found] ` <119aab440907131124r3fd333d3n967cdde2cf3c2e1b@mail.gmail.com>
[not found] ` <20090713211723.GE10110@hall.aurel32.net>
2009-07-13 22:16 ` Help on memchr() EGLIBC assembly code Matt Turner
2009-07-13 22:24 ` Aurelien Jarno
2009-07-15 19:48 ` Richard Henderson
2009-07-19 14:29 ` Aurelien Jarno [this message]
2009-07-26 23:45 ` Aurelien Jarno
2009-07-27 9:29 ` Aurelien Jarno
2009-07-30 0:24 ` Richard Henderson
2009-07-30 16:29 ` Aurelien Jarno
2009-07-31 23:25 ` Richard Henderson
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