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Subject: Re: [HW_RNG] How to use generic rng in kernel space
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: moreau francis <francis_moreau2000@yahoo.fr>
Cc: mb@bu3sch.de, linux-kernel@vger.kernel.org
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Date: Tue, 01 Aug 2006 14:29:54 +0100
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Ar Maw, 2006-08-01 am 12:09 +0000, ysgrifennodd moreau francis:
> Another question about the implementation. If O_NONBLOCK
> flag is passed when opening /dev/hw_random, how does the
> read method ensure that the caller won't sleep since it calls
> mutex_lock_interruptible() function unconditiannaly ? I must
> miss something but don't know what...

O_NONBLOCK doesn't necessarily imply "never sleep", it implies "don't
sleep waiting for an event/long time". So where the mutex is just
serializing access to hardware that will be very brief it is fine not to
check O_NONBLOCK/FNDELAY.