From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Junio C Hamano <junkio@cox.net>,
git@vger.kernel.org, Linus Torvalds <torvalds@osdl.org>
Subject: Re: First cut at git port to Cygwin
Date: Mon, 10 Oct 2005 21:42:49 +0200 (CEST) [thread overview]
Message-ID: <Pine.LNX.4.63.0510102139540.7861@wbgn013.biozentrum.uni-wuerzburg.de> (raw)
In-Reply-To: <434AC058.60803@zytor.com>
Hi,
On Mon, 10 Oct 2005, H. Peter Anvin wrote:
> Johannes Schindelin wrote:
> >
> > > Junio C Hamano wrote:
> > >
> > > > PROT_WRITE is true, but we do MAP_PRIVATE, and if I recall
> > > > correctly we do not write file via mmap -- at least we do not
> > > > intend to.
> > > >
> > >
> > > Then PROT_READ probably makes more sense?
> >
> > Not necessarily. Sometimes you need to annotate the data from the index, and
> > this does not need to be written back to the index file.
> >
>
> In the above sentence, emphasis on "at least we do not intend to." If writes
> are done legitimately then that's fine, but we shouldn't have "accidental
> writes" -- those would be program bugs!
Yes, those would be bugs. However, if I understood the man page for mmap()
correctly, then PROT_WRITE && MAP_PRIVATE makes the data copy-on-write,
which means that those bugs would have been found (because the changes
would no longer be present when git was called the next time). And I
checked: all mmap() calls in git are MAP_PRIVATE.
> > > > Yes. It might have been overkill that you supported writing
> > > > changes back, though.
> > >
> > > Not just overkill; if we do MAP_PRIVATE it's actively WRONG.
> >
> > See above.
> >
>
> Eh? If we MAP_PRIVATE, *and* we (intentionally) write to it, we *BETTER* not
> write anything back.
Yes. That was *my* mistake.
Ciao,
Dscho
next prev parent reply other threads:[~2005-10-10 19:42 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-29 0:53 First cut at git port to Cygwin H. Peter Anvin
2005-09-29 4:30 ` Junio C Hamano
2005-09-29 5:07 ` H. Peter Anvin
2005-09-29 4:46 ` Martin Langhoff
2005-09-29 5:13 ` Junio C Hamano
2005-09-29 6:19 ` H. Peter Anvin
2005-09-29 8:46 ` Johannes Schindelin
2005-09-29 16:11 ` H. Peter Anvin
2005-09-29 17:25 ` H. Peter Anvin
2005-09-30 10:02 ` Junio C Hamano
2005-09-30 17:01 ` H. Peter Anvin
2005-09-30 19:08 ` H. Peter Anvin
2005-10-04 12:31 ` Alex Riesen
2005-10-04 13:06 ` Alex Riesen
2005-10-04 14:06 ` H. Peter Anvin
2005-10-05 3:15 ` Christopher Faylor
2005-10-04 15:03 ` H. Peter Anvin
2005-10-05 3:16 ` Christopher Faylor
2005-10-05 5:25 ` H. Peter Anvin
2005-10-05 11:24 ` Alex Riesen
2005-10-05 15:46 ` Alex Riesen
2005-10-05 15:54 ` Christopher Faylor
2005-10-05 16:09 ` Davide Libenzi
2005-10-05 16:15 ` Christopher Faylor
2005-10-05 16:23 ` H. Peter Anvin
2005-10-05 16:28 ` Christopher Faylor
2005-10-05 17:29 ` Davide Libenzi
2005-10-05 19:17 ` Alex Riesen
2005-10-05 20:29 ` Christopher Faylor
2005-10-06 9:05 ` Alex Riesen
2005-10-06 10:07 ` Alex Riesen
2005-10-07 12:44 ` Alex Riesen
2005-10-07 15:34 ` Linus Torvalds
2005-10-07 20:54 ` Alex Riesen
2005-10-07 21:22 ` Alex Riesen
2005-10-07 21:29 ` Chuck Lever
2005-10-07 21:39 ` Alex Riesen
2005-10-08 16:11 ` Linus Torvalds
2005-10-08 17:38 ` Elfyn McBratney
2005-10-08 17:43 ` Elfyn McBratney
2005-10-08 18:27 ` Johannes Schindelin
2005-10-08 18:44 ` Junio C Hamano
2005-10-08 19:04 ` Johannes Schindelin
2005-10-08 21:10 ` Junio C Hamano
2005-10-08 22:06 ` Johannes Schindelin
2005-10-10 18:43 ` H. Peter Anvin
2005-10-10 19:01 ` Johannes Schindelin
2005-10-10 19:26 ` H. Peter Anvin
2005-10-10 19:42 ` Johannes Schindelin [this message]
2005-10-10 20:21 ` Junio C Hamano
2005-10-10 20:34 ` Junio C Hamano
2005-10-10 20:52 ` H. Peter Anvin
2005-10-10 20:27 ` Daniel Barkalow
2005-10-08 18:49 ` Alex Riesen
2005-10-09 20:40 ` Commit text BEFORE the dashes (Re: First cut at git port to Cygwin) Matthias Urlichs
[not found] ` <7vfyrdyre5.fsf@assigned-by-dhcp.cox.net>
2005-10-07 23:45 ` First cut at git port to Cygwin Alex Riesen
2005-10-08 1:00 ` Elfyn McBratney
2005-10-10 18:45 ` H. Peter Anvin
2005-10-05 13:16 ` Jonas Fonseca
2005-10-05 13:58 ` Johannes Schindelin
2005-10-05 15:52 ` [PATCH] Fix symbolic ref validation Jonas Fonseca
2005-10-05 16:54 ` Junio C Hamano
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