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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: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2013-09-12 14:27:22 -04:00
parent 5910895f0e
commit 3ef4cb2d65
1 changed files with 10 additions and 4 deletions
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14
drivers/char/random.c
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@ -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);