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>
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 80b5877..89eb5a8 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -710,12 +710,18 @@
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);