Re: [V4L] races in v4l read + write in 2.4

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On Monday 30 October 2000 19:46, Alan Cox wrote:
> > Does this mean that someone should go over all video drivers and put
> > locks into them ?
>
> If appropriate - you need locks anyway you can open once and read/write in
> parallel in threaded apps

Exactly for this reason I've made a patch, that takes a semaphore in read() 
and write().
Isn't the path important for performance the mmap() path ?
Thus semaphores in read & write kill a whole number of races
with a very small impact on performance.

I could take out the exclusive open part or make it depend on a flag provided 
by the driver, if you think this to be important. But, frankly, I see no 
devices that would profit from that. Even radio cards can listen on one 
frequency if I am not mistaken.

	Regards
		Oliver





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