Commit 3ef4cb2d authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

random: optimize spinlock use in add_device_randomness() 



The add_device_randomness() function calls mix_pool_bytes() twice for
the input pool and the non-blocking pool, for a total of four times.
By using _mix_pool_byte() and taking the spinlock in
add_device_randomness(), we can halve the number of times we need
take each pool's spinlock.

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 5910895f

drivers/char/random.c

+10 −4
Original line number Diff line number Diff line
@@ -710,12 +710,18 @@ struct timer_rand_state { 
void add_device_randomness(const void *buf, unsigned int size)

{

	unsigned long time = random_get_entropy() ^ jiffies;

	unsigned long flags;



	trace_add_device_randomness(size, _RET_IP_);

	mix_pool_bytes(&input_pool, buf, size, NULL);

	mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);

	mix_pool_bytes(&nonblocking_pool, buf, size, NULL);

	mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);

	spin_lock_irqsave(&input_pool.lock, flags);

	_mix_pool_bytes(&input_pool, buf, size, NULL);

	_mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);

	spin_unlock_irqrestore(&input_pool.lock, flags);



	spin_lock_irqsave(&nonblocking_pool.lock, flags);

	_mix_pool_bytes(&nonblocking_pool, buf, size, NULL);

	_mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);

	spin_unlock_irqrestore(&nonblocking_pool.lock, flags);

}

EXPORT_SYMBOL(add_device_randomness);

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