Re: Concurrent access to /dev/urandom

[Matt Mackall]

On Thu, Dec 09, 2004 at 10:46:30AM +0800, andyliu wrote:
> hi Ted
> 
>    i think this is better than use the spin lock.
>   but i think maybe there should put an #ifdef SMP :)
> just like
> 
> #ifdef CONFIG_SMP
>                tmp[0] = 0x67452301 ^ smp_processor_id();
>                tmp[1] = 0xefcdab89 ^ (__u32) current;
>                tmp[2] = 0x98badcfe ^ preempt_count();
> #endif
> 
> is it needed? 

The race can be hit with get_random_bytes on UP if we get
interrupted/preempted between hashing and mixing. Which is why
preempt_count is useful..

-- 
Mathematics is the supreme nostalgia of our time.
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