LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Jeff Dike <jdike@addtoit.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: andi@firstfloor.org, harvey.harrison@gmail.com,
	akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	user-mode-linux-devel@lists.sourceforge.net
Subject: Re: uml and -regparm=3
Date: Wed, 9 Jan 2008 21:14:04 -0500	[thread overview]
Message-ID: <20080110021404.GA11287@c2.user-mode-linux.org> (raw)
In-Reply-To: <E1JCioy-0006os-6i@pomaz-ex.szeredi.hu>

On Wed, Jan 09, 2008 at 10:50:48PM +0100, Miklos Szeredi wrote:
> > FASTCALL is useless and should not make a difference. It enables
> > regparm on specific functions, but that should not make a difference
> > if it works or not.
> 
> __down_write() in include/asm-x86/rwsem.h seems to assume, that the
> semaphore pointer is passed in %eax down to rwsem_down_write_failed(),
> so regparm does make a difference there.

And rwsem_down_write_failed seems to think it's getting the pointer in
%eax:

Dump of assembler code for function rwsem_down_write_failed:
0x08193599 <rwsem_down_write_failed+0>: push   %ebp
0x0819359a <rwsem_down_write_failed+1>: mov    %esp,%ebp
0x0819359c <rwsem_down_write_failed+3>: push   %ebx
0x0819359d <rwsem_down_write_failed+4>: mov    %eax,%ebx
0x0819359f <rwsem_down_write_failed+6>: sub    $0x10,%esp
0x081935a2 <rwsem_down_write_failed+9>: push   $0xffffffff
0x081935a4 <rwsem_down_write_failed+11>:        lea    0xffffffec(%ebp),%eax
0x081935a7 <rwsem_down_write_failed+14>:        push   %eax
0x081935a8 <rwsem_down_write_failed+15>:        push   %ebx
0x081935a9 <rwsem_down_write_failed+16>:        movl   $0x2,0xfffffff8(%ebp)
0x081935b0 <rwsem_down_write_failed+23>:        call   0x8193423 <rwsem_down_failed_common>

This is clearly taking something from %eax and something on the stack
(and a -1) and passing it to rwsem_down_failed_common, corresponding
to this:
	rwsem_down_failed_common(sem, &waiter,
				RWSEM_WAITING_BIAS - RWSEM_ACTIVE_BIAS);

So, this does look right to me.

				Jeff

-- 
Work email - jdike at linux dot intel dot com

  reply	other threads:[~2008-01-10  2:14 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-09 21:01 Miklos Szeredi
2008-01-09 21:12 ` Andi Kleen
2008-01-09 21:20   ` Miklos Szeredi
2008-01-09 21:32     ` Andi Kleen
2008-01-09 21:50       ` Miklos Szeredi
2008-01-10  2:14         ` Jeff Dike [this message]
2008-01-10  2:37           ` Andi Kleen
2008-01-10  2:45             ` H. Peter Anvin
2008-01-09 21:33     ` Adrian Bunk
2008-01-09 22:01 ` linux-os (Dick Johnson)
2008-01-10  7:32 ` Ingo Molnar
2008-01-10  9:05   ` Miklos Szeredi
2008-01-10  9:35     ` Ingo Molnar

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080110021404.GA11287@c2.user-mode-linux.org \
    --to=jdike@addtoit.com \
    --cc=akpm@linux-foundation.org \
    --cc=andi@firstfloor.org \
    --cc=harvey.harrison@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=miklos@szeredi.hu \
    --cc=user-mode-linux-devel@lists.sourceforge.net \
    --subject='Re: uml and -regparm=3' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).