From: Oleg Nesterov <oleg@redhat.com>
To: Vasiliy Kulikov <segoon@openwall.com>
Cc: Manuel Lauss <manuel.lauss@googlemail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Richard Weinberger <richard@nod.at>,
Marc Zyngier <marc.zyngier@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] shm: optimize exit_shm()
Date: Wed, 3 Aug 2011 21:29:30 +0200 [thread overview]
Message-ID: <20110803192930.GA320@redhat.com> (raw)
In-Reply-To: <20110803191639.GA6306@albatros>
On 08/03, Vasiliy Kulikov wrote:
>
> On Wed, Aug 03, 2011 at 21:08 +0200, Manuel Lauss wrote:
> > > +
> > > /* Destroy all already created segments, but not mapped yet */
> > > down_write(&shm_ids(ns).rw_mutex);
> > > if (shm_ids(ns).in_use)
> >
> > This check here is now unnecessary, yes?
>
> No, as I said in the comment above, other task may be holding the mutex and
> deleting the last shm segment. So, current task will see in_use == 1
> before down_write(), but == 0 after it.
And? Why we can not do idr_for_each() in this (unikely) case?
> > And this also fixes the oops.
>
> Yes, but it only hides the real problem - tasks' dependency on initialized
> init_*_ns.
This is true, but your patch has the same dependency, but pretends
it doesn't ;) and it complicates the code.
Oleg.
next prev parent reply other threads:[~2011-08-03 19:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-03 14:04 + shm-fix-a-race-between-shm_exit-and-shm_init.patch added to -mm tree Oleg Nesterov
2011-08-03 18:24 ` Vasiliy Kulikov
2011-08-03 18:26 ` [PATCH] shm: fix wrong tests Vasiliy Kulikov
2011-08-03 18:28 ` [PATCH] shm: optimize exit_shm() Vasiliy Kulikov
2011-08-03 19:08 ` Manuel Lauss
2011-08-03 19:16 ` Vasiliy Kulikov
2011-08-03 19:29 ` Oleg Nesterov [this message]
2011-08-03 19:41 ` Vasiliy Kulikov
2011-08-03 19:43 ` Oleg Nesterov
2011-08-03 19:21 ` Oleg Nesterov
2011-08-03 19:34 ` Vasiliy Kulikov
2011-08-03 19:39 ` Oleg Nesterov
2011-08-03 19:18 ` + shm-fix-a-race-between-shm_exit-and-shm_init.patch added to -mm tree Oleg Nesterov
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