From: Andrew Morton <akpm@linux-foundation.org>
To: Nikanth Karthikesan <knikanth@novell.com>
Cc: Jens Axboe <jens.axboe@oracle.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][RFC] Handle improbable possibility of io_context->refcount overflow
Date: Wed, 29 Apr 2009 00:59:30 -0700 [thread overview]
Message-ID: <20090429005930.3752dd6d.akpm@linux-foundation.org> (raw)
In-Reply-To: <200904291221.40361.knikanth@novell.com>
On Wed, 29 Apr 2009 12:21:39 +0530 Nikanth Karthikesan <knikanth@novell.com> wrote:
> Hi Jens
>
> Currently io_context has an atomic_t(int) as refcount. In case of cfq, for
> each device a task does I/O, a reference to the io_context would be taken. And
> when there are multiple process sharing io_contexts(CLONE_IO) would also have
> a reference to the same io_context. Theoretically the possible maximum number
> of processes sharing the same io_context + the number of disks/cfq_data
> referring to the same io_context can overflow the 32-bit counter on a very
> high-end machine. Even though it is an improbable case, let us make it
> difficult by changing the refcount to atomic64_t(long).
>
Sorry, atomic64_t isn't implemented on 32 bit architectures.
Perhaps it should be, but I expect it'd be pretty slow.
next prev parent reply other threads:[~2009-04-29 8:01 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-29 6:51 [PATCH][RFC] Handle improbable possibility of io_context->refcount overflow Nikanth Karthikesan
2009-04-29 7:59 ` Andrew Morton [this message]
2009-04-29 10:03 ` Nikanth Karthikesan
2009-04-29 15:15 ` Andrew Morton
2009-04-30 7:28 ` Nikanth Karthikesan
2009-04-30 7:28 ` [PATCH v2] " Nikanth Karthikesan
2009-04-30 7:29 ` [PATCH] Detect and warn on atomic_inc/atomic_dec wrapping around Nikanth Karthikesan
2009-04-30 8:23 ` Ingo Molnar
2009-04-30 10:11 ` Nikanth Karthikesan
2009-04-30 10:47 ` Ingo Molnar
2009-04-30 12:08 ` Nikanth Karthikesan
2009-04-30 12:21 ` Ingo Molnar
2009-04-30 12:26 ` Nikanth Karthikesan
2009-04-30 12:50 ` Ingo Molnar
2009-04-30 13:29 ` Nikanth Karthikesan
2009-04-30 13:37 ` Ingo Molnar
2009-04-30 13:51 ` Nikanth Karthikesan
2009-04-30 14:05 ` Ingo Molnar
2009-04-30 14:09 ` Nikanth Karthikesan
2009-04-30 14:44 ` Ingo Molnar
2009-04-30 21:45 ` Andrew Morton
2009-05-01 4:57 ` Nikanth Karthikesan
2009-05-01 5:06 ` Andrew Morton
2009-05-01 5:13 ` Andrew Morton
2009-05-08 0:23 ` Andrew Morton
2009-05-08 10:40 ` Nikanth Karthikesan
2009-05-08 10:46 ` Nikanth Karthikesan
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