From: Andrea Arcangeli <aarcange@redhat.com>
To: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>, Rik van Riel <riel@redhat.com>,
Chris Wright <chrisw@redhat.com>,
Nick Piggin <nickpiggin@yahoo.com.au>,
Andrew Morton <akpm@linux-foundation.org>,
"Justin M. Forbes" <jmforbes@linuxtx.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 13/12] ksm: fix munlock during exit_mmap deadlock
Date: Tue, 25 Aug 2009 20:10:19 +0200 [thread overview]
Message-ID: <20090825181019.GT14722@random.random> (raw)
In-Reply-To: <Pine.LNX.4.64.0908251836050.30372@sister.anvils>
On Tue, Aug 25, 2009 at 06:49:09PM +0100, Hugh Dickins wrote:
> Sorry, I just don't get it. How does down_read here help?
> Perhaps you thought ksm.c had down_write of mmap_sem in all cases?
>
> No, and I don't think we want to change its down_reads to down_writes.
Looking ksm.c it should have been down_write indeed...
> Nor do we want to change your down_read here to down_write, that will
> just reintroduce the OOM deadlock that 9/12 was about solving.
I'm not sure anymore I get what this fix is about... mm_users is
allowed to go to 0. If mm_users is allowed to go to 0, it's up to ksm
to check inside its inner loops that mm_users is 0 and bail
out. Bailing out it will unblock exit so that exit_mmap can run. What
exactly is the unfixable issue?
WARNING: multiple messages have this Message-ID (diff)
From: Andrea Arcangeli <aarcange@redhat.com>
To: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>, Rik van Riel <riel@redhat.com>,
Chris Wright <chrisw@redhat.com>,
Nick Piggin <nickpiggin@yahoo.com.au>,
Andrew Morton <akpm@linux-foundation.org>,
"Justin M. Forbes" <jmforbes@linuxtx.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 13/12] ksm: fix munlock during exit_mmap deadlock
Date: Tue, 25 Aug 2009 20:10:19 +0200 [thread overview]
Message-ID: <20090825181019.GT14722@random.random> (raw)
In-Reply-To: <Pine.LNX.4.64.0908251836050.30372@sister.anvils>
On Tue, Aug 25, 2009 at 06:49:09PM +0100, Hugh Dickins wrote:
> Sorry, I just don't get it. How does down_read here help?
> Perhaps you thought ksm.c had down_write of mmap_sem in all cases?
>
> No, and I don't think we want to change its down_reads to down_writes.
Looking ksm.c it should have been down_write indeed...
> Nor do we want to change your down_read here to down_write, that will
> just reintroduce the OOM deadlock that 9/12 was about solving.
I'm not sure anymore I get what this fix is about... mm_users is
allowed to go to 0. If mm_users is allowed to go to 0, it's up to ksm
to check inside its inner loops that mm_users is 0 and bail
out. Bailing out it will unblock exit so that exit_mmap can run. What
exactly is the unfixable issue?
--
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next prev parent reply other threads:[~2009-08-25 18:14 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-03 12:08 [PATCH 0/12] ksm: stats, oom, doc, misc Hugh Dickins
2009-08-03 12:08 ` Hugh Dickins
2009-08-03 12:10 ` [PATCH 1/12] ksm: rename kernel_pages_allocated Hugh Dickins
2009-08-03 12:10 ` Hugh Dickins
2009-08-03 14:21 ` Izik Eidus
2009-08-03 14:21 ` Izik Eidus
2009-08-03 16:48 ` Andrea Arcangeli
2009-08-03 16:48 ` Andrea Arcangeli
2009-08-03 12:11 ` [PATCH 2/12] ksm: move pages_sharing updates Hugh Dickins
2009-08-03 12:11 ` Hugh Dickins
2009-08-03 14:34 ` Izik Eidus
2009-08-03 14:34 ` Izik Eidus
2009-08-03 16:53 ` Andrea Arcangeli
2009-08-03 16:53 ` Andrea Arcangeli
2009-08-03 17:34 ` Hugh Dickins
2009-08-03 17:34 ` Hugh Dickins
2009-08-03 12:11 ` [PATCH 3/12] ksm: pages_unshared and pages_volatile Hugh Dickins
2009-08-03 12:11 ` Hugh Dickins
2009-08-03 14:54 ` Izik Eidus
2009-08-03 14:54 ` Izik Eidus
2009-08-04 21:49 ` Andrew Morton
2009-08-04 21:49 ` Andrew Morton
2009-08-05 11:39 ` Hugh Dickins
2009-08-05 11:39 ` Hugh Dickins
2009-08-05 15:11 ` Andrea Arcangeli
2009-08-05 15:11 ` Andrea Arcangeli
2009-08-03 12:12 ` [PATCH 4/12] ksm: break cow once unshared Hugh Dickins
2009-08-03 12:12 ` Hugh Dickins
2009-08-03 16:00 ` Izik Eidus
2009-08-03 16:00 ` Izik Eidus
2009-08-03 12:14 ` [PATCH 5/12] ksm: keep quiet while list empty Hugh Dickins
2009-08-03 12:14 ` Hugh Dickins
2009-08-03 16:55 ` Izik Eidus
2009-08-03 16:55 ` Izik Eidus
2009-08-04 21:59 ` Andrew Morton
2009-08-04 21:59 ` Andrew Morton
2009-08-05 11:54 ` Hugh Dickins
2009-08-05 11:54 ` Hugh Dickins
2009-08-03 12:15 ` [PATCH 6/12] ksm: five little cleanups Hugh Dickins
2009-08-03 12:15 ` Hugh Dickins
2009-08-04 12:41 ` Izik Eidus
2009-08-04 12:41 ` Izik Eidus
2009-08-03 12:16 ` [PATCH 7/12] ksm: fix endless loop on oom Hugh Dickins
2009-08-03 12:16 ` Hugh Dickins
2009-08-04 12:55 ` Izik Eidus
2009-08-04 12:55 ` Izik Eidus
2009-08-03 12:17 ` [PATCH 8/12] ksm: distribute remove_mm_from_lists Hugh Dickins
2009-08-03 12:17 ` Hugh Dickins
2009-08-04 13:03 ` Izik Eidus
2009-08-04 13:03 ` Izik Eidus
2009-08-03 12:18 ` [PATCH 9/12] ksm: fix oom deadlock Hugh Dickins
2009-08-03 12:18 ` Hugh Dickins
2009-08-04 19:32 ` Izik Eidus
2009-08-04 19:32 ` Izik Eidus
2009-08-25 14:58 ` Andrea Arcangeli
2009-08-25 14:58 ` Andrea Arcangeli
2009-08-25 15:22 ` [PATCH 13/12] ksm: fix munlock during exit_mmap deadlock Andrea Arcangeli
2009-08-25 15:22 ` Andrea Arcangeli
2009-08-25 17:49 ` Hugh Dickins
2009-08-25 17:49 ` Hugh Dickins
2009-08-25 18:10 ` Andrea Arcangeli [this message]
2009-08-25 18:10 ` Andrea Arcangeli
2009-08-25 18:58 ` Hugh Dickins
2009-08-25 18:58 ` Hugh Dickins
2009-08-25 19:45 ` Andrea Arcangeli
2009-08-25 19:45 ` Andrea Arcangeli
2009-08-26 16:18 ` Justin M. Forbes
2009-08-26 16:18 ` Justin M. Forbes
2009-08-26 19:17 ` Hugh Dickins
2009-08-26 19:17 ` Hugh Dickins
2009-08-26 19:44 ` Andrea Arcangeli
2009-08-26 19:44 ` Andrea Arcangeli
2009-08-26 19:57 ` Hugh Dickins
2009-08-26 19:57 ` Hugh Dickins
2009-08-26 20:28 ` Andrea Arcangeli
2009-08-26 20:28 ` Andrea Arcangeli
2009-08-26 20:54 ` Izik Eidus
2009-08-26 20:54 ` Izik Eidus
2009-08-26 21:14 ` Andrea Arcangeli
2009-08-26 21:14 ` Andrea Arcangeli
2009-08-26 21:49 ` Izik Eidus
2009-08-26 21:49 ` Izik Eidus
2009-08-27 19:11 ` Hugh Dickins
2009-08-27 19:11 ` Hugh Dickins
2009-08-27 19:35 ` Izik Eidus
2009-08-27 19:35 ` Izik Eidus
2009-08-26 22:00 ` David Rientjes
2009-08-26 22:00 ` David Rientjes
2009-08-26 20:29 ` Hugh Dickins
2009-08-26 20:29 ` Hugh Dickins
2009-08-25 17:35 ` [PATCH 9/12] ksm: fix oom deadlock Hugh Dickins
2009-08-25 17:35 ` Hugh Dickins
2009-08-25 17:47 ` Andrea Arcangeli
2009-08-25 17:47 ` Andrea Arcangeli
2009-08-03 12:19 ` [PATCH 10/12] ksm: sysfs and defaults Hugh Dickins
2009-08-03 12:19 ` Hugh Dickins
2009-08-04 19:34 ` Izik Eidus
2009-08-04 19:34 ` Izik Eidus
2009-08-03 12:21 ` [PATCH 11/12] ksm: add some documentation Hugh Dickins
2009-08-03 12:21 ` Hugh Dickins
2009-08-04 19:35 ` Izik Eidus
2009-08-04 19:35 ` Izik Eidus
2009-08-03 12:22 ` [PATCH 12/12] ksm: remove VM_MERGEABLE_FLAGS Hugh Dickins
2009-08-03 12:22 ` Hugh Dickins
2009-08-04 19:35 ` Izik Eidus
2009-08-04 19:35 ` Izik Eidus
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