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Message-Id: <20090318.094935.238694196.nemoto@toshiba-tops.co.jp>
Date: Wed, 18 Mar 2009 09:49:35 +0900 (JST)
From: Atsushi Nemoto <anemo@....ocn.ne.jp>
To: dan.j.williams@...el.com
Cc: linux-mips@...ux-mips.org, ralf@...ux-mips.org,
linux-kernel@...r.kernel.org, haavard.skinnemoen@...el.com
Subject: Re: [PATCH 1/2] dmaengine: TXx9 Soc DMA Controller driver
On Tue, 17 Mar 2009 10:02:14 -0700, Dan Williams <dan.j.williams@...el.com> wrote:
> >> The sysfs device has a longer lifetime than dma_device. See commit
> >> 41d5e59c [1].
> >
> > The sysfs device for dma_chan (dma_chan_dev) has a shorter lifetime
> > than dma_device, doesn't it?
>
> No, dma_async_device_unregister(), and the freeing of dma_device, may
> finish before chan_dev_release is called. Userspace gates the final
> release of dma_chan_dev objects.
You mean, if the sysfs device file was opened when
dma_async_device_unregister() was called, the sysfs device will not be
released until the sysfs device file is closed, right? If so I can
see.
BTW, there are another holes in dma_async_device_register. If
idr_pre_get or idr_get_new was failed, idr_ref will not be freed.
---
Atsushi Nemoto
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