From: Martyn Welch <martyn.welch@ge.com>
To: "Emilio G. Cota" <cota@braap.org>
Cc: devel@driverdev.osuosl.org, Manohar Vanga <manohar.vanga@cern.ch>,
gregkh@suse.de, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/5] staging: vme: add functions for bridge module refcounting
Date: Fri, 19 Aug 2011 09:42:14 +0100 [thread overview]
Message-ID: <4E4E21E6.3050400@ge.com> (raw)
In-Reply-To: <4E4E1F89.4070702@ge.com>
On 19/08/11 09:32, Martyn Welch wrote:
> On 13/08/11 09:54, Emilio G. Cota wrote:
>> On Fri, Aug 12, 2011 at 12:30:49 +0200, Manohar Vanga wrote:
>>> This patch adds functions that allow for reference counting
>>> bridge modules. The patch introduces the functions
>>> 'vme_bridge_get()' and 'vme_bridge_put()'.
>> (snip)
>>> +int vme_bridge_get(unsigned int bus_id)
>> (snip)
>>> +void vme_bridge_put(struct vme_bridge *bridge)
>>
>> Note the input parameter imbalance; in fact this is serious
>> (see my email on patch 5) because _get() needs to acquire
>> vme_buses_lock, whereas _put() doesn't. Since a caller with
>> bridge has bridge->num, but the opposite doesn't hold (num
>> doesn't give you the bridge without acquiring vme_buses_lock),
>> it seems reasonable to me to take the bus_id as the input for
>> both functions, because the requirements on the caller are lower.
>>
>
> Patch 4 makes changes the struct vme_bridge to struct vme_dev. Looking at the
> callers we are then effectively doing:
>
Patch 5 even.
Martyn
> vme_bridge_get(vme_dev.id)
>
> Then in vme_bridge_get(), looping through all the buses to find the one with
> the correct id...
>
> We could just pass in the struct vme_dev to both functions.
>
> Martyn
>
>> But the locking needs to be handled with care, see my reply
>> to patch 5.
>>
>> Emilio
>>
>> _______________________________________________
>> devel mailing list
>> devel@linuxdriverproject.org
>> http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
>
>
--
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GE Intelligent Platforms | Wales (3828642) at 100
T +44(0)127322748 | Barbirolli Square, Manchester,
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next prev parent reply other threads:[~2011-08-19 8:42 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-12 10:30 [PATCH 0/5] [RESEND v2] VME Framework Fixes Manohar Vanga
2011-08-12 10:30 ` [PATCH 1/5] staging: vme: make [alloc|free]_consistent bridge specific Manohar Vanga
2011-08-16 8:15 ` Martyn Welch
2011-08-12 10:30 ` [PATCH 2/5] staging: vme: keep track of registered buses Manohar Vanga
2011-08-16 8:16 ` Martyn Welch
2011-08-12 10:30 ` [PATCH 3/5] staging: vme: add functions for bridge module refcounting Manohar Vanga
2011-08-13 7:47 ` Emilio G. Cota
2011-08-15 10:05 ` Manohar Vanga
2011-08-15 18:49 ` Emilio G. Cota
2011-08-22 12:24 ` Martyn Welch
2011-08-23 9:09 ` Manohar Vanga
2011-08-13 8:54 ` Emilio G. Cota
2011-08-19 8:32 ` Martyn Welch
2011-08-19 8:42 ` Martyn Welch [this message]
2011-08-12 10:30 ` [PATCH 4/5] staging: vme: add struct vme_dev for VME devices Manohar Vanga
2011-08-12 10:30 ` [PATCH 5/5] staging: vme: make match() driver specific to improve non-VME64x support Manohar Vanga
2011-08-13 8:50 ` Emilio G. Cota
2011-08-23 22:14 ` [PATCH 0/5] [RESEND v2] VME Framework Fixes Greg KH
2011-08-24 7:40 ` Martyn Welch
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