From: Linus Torvalds <torvalds@linux-foundation.org>
To: Michal Hocko <mhocko@suse.cz>
Cc: linux-mm <linux-mm@kvack.org>, Cyril Hrubis <chrubis@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Michel Lespinasse <walken@google.com>,
Rik van Riel <riel@redhat.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: Should mmap MAP_LOCKED fail if mm_poppulate fails?
Date: Tue, 28 Apr 2015 09:57:11 -0700 [thread overview]
Message-ID: <CA+55aFydkG-BgZzry5DrTzueVh9VvEcVJdLV8iOyUphQk=0vpw@mail.gmail.com> (raw)
In-Reply-To: <20150428164302.GI2659@dhcp22.suse.cz>
On Tue, Apr 28, 2015 at 9:43 AM, Michal Hocko <mhocko@suse.cz> wrote:
>
> Hmm, no other thread has the address from the current mmap call except
> for MAP_FIXED (more on that below).
With things like opportunistic SIGSEGV handlers that map/unmap things
as the user takes faults, that's actually not at all guaranteed.
Yeah, it's unusual, but I've seen it, with threaded applications where
people play games with user-space memory management, and do "demand
allocation" with mmap() in response to signals.
Admittedly we already do bad things in mmap(MAP_FIXED) for that case,
since we dropped the vm lock. But at least it shouldn't be any worse
than a thread speculatively touching the pages..
Linus
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next prev parent reply other threads:[~2015-04-28 16:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-14 9:50 Michal Hocko
2015-04-28 12:11 ` Michal Hocko
2015-04-28 12:11 ` [RFC 1/3] mm: mmap make MAP_LOCKED really mlock semantic Michal Hocko
2015-04-28 23:10 ` Andrew Morton
2015-04-29 7:52 ` Michal Hocko
2015-04-28 12:11 ` [RFC 2/3] mm: allow munmap related functions to understand gfp_mask Michal Hocko
2015-04-28 12:11 ` [RFC 3/3] mm: introduce do_munmap_nofail Michal Hocko
2015-04-28 16:01 ` Should mmap MAP_LOCKED fail if mm_poppulate fails? Linus Torvalds
2015-04-28 16:43 ` Michal Hocko
2015-04-28 16:57 ` Linus Torvalds [this message]
2015-04-28 18:35 ` Michal Hocko
2015-04-28 18:38 ` Linus Torvalds
2015-04-28 20:36 ` Michal Hocko
2015-04-29 11:38 ` [RFC PATCH] mmap.2: clarify MAP_LOCKED semantic (was: Re: Should mmap MAP_LOCKED fail if mm_poppulate fails?) Michal Hocko
2015-04-30 0:28 ` David Rientjes
2015-04-30 14:52 ` Michal Hocko
2015-05-06 12:21 ` Michal Hocko
2015-04-28 20:21 ` Should mmap MAP_LOCKED fail if mm_poppulate fails? Michal Hocko
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