From: "Stephen C. Tweedie" <sct@redhat.com>
To: Colin Plumb <colin@nyx.net>
Cc: sct@redhat.com, linux-mm@kvack.orgStephen Tweedie <sct@redhat.com>
Subject: Re: Why don't shared anonymous mappings work?
Date: Tue, 19 Jan 1999 14:32:34 GMT [thread overview]
Message-ID: <199901191432.OAA05326@dax.scot.redhat.com> (raw)
In-Reply-To: <199901132131.OAA09149@nyx10.nyx.net>
Hi,
On Wed, 13 Jan 1999 14:31:41 -0700 (MST), Colin Plumb <colin@nyx.net>
said:
> Um, I just thought of another problem with shared anonymous pages.
> It's similar to the zero-page issue you raised, but it's no longer
> a single special case.
> Copy-on-write and shared mappings. Let's say that process 1 has a COW
> copy of page X. Then the page is shared (via mmap /proc/1/mem or some
> such) with process 2. Now process A writes to the page.
Invalid argument. This is *precisely* why mmap of /proc/X/mem is
broken. We don't need to implement reasonable semantics for that case,
because there _are_ no reasonable semantics for a page which can be both
MAP_PRIVATE and MAP_SHARED in the same process.
--Stephen
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next prev parent reply other threads:[~1999-01-19 14:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-01-13 21:31 Colin Plumb
1999-01-19 14:32 ` Stephen C. Tweedie [this message]
1999-01-19 15:23 ` Eric W. Biederman
-- strict thread matches above, loose matches on Subject: below --
1999-01-15 6:43 Colin Plumb
1999-01-14 3:07 Colin Plumb
1999-01-15 6:07 ` Benjamin C.R. LaHaise
[not found] <199901061523.IAA14788@nyx10.nyx.net>
1999-01-06 19:51 ` Eric W. Biederman
1999-01-07 5:55 ` Eric W. Biederman
1999-01-13 20:21 ` Stephen C. Tweedie
1999-01-05 12:51 Colin Plumb
1999-01-06 4:05 ` Eric W. Biederman
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