Re: [PATCH v3] USB: prevent overlapping access by usb-storage and usbfs

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Hello.

On 01/18/2013 10:51 PM, Greg KH wrote:

>> +	/*
>> +	 * This is our custom open-coded lock, similar to r/w locks in concept.
>> +	 * It prevents usb-storage, usbfs, and /proc from simultaneous access.
>> +	 */
>> +	wait_queue_head_t excl_wait;
>> +	spinlock_t excl_lock;
>> +	unsigned int excl_type;
> 
> I _really_ don't like open-coded locks, and given the wide range of
> existing kernel primitives, surely something that we already have can
> work here as well, right?

   I'm not so sure. Not that I'm familiar with all the primitives but I think
this open coded lock was used for a good reason.

> I don't want to be maintaining this custom
> lock code for the next 20+ years, ensuring that it stays working
> properly under all conditions, do you?

> So, any chance to use something non-custom?

   Unfortunately, I'm totally out of time at this point. Let's see if I can
return to this in a month's time or so. I'd also appreciate any ideas about
existing primitives (rwlock_t seems closest but it can't have 3rd, exclusive
state, AFAIR).

> thanks,

> greg k-h

WBR, Sergei

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