[PATCH, RFC 06/12] random: optimize spinlock use in add_device_randomness()

[Theodore Ts'o]

No point taking the spinlock twice for each call to mix_pool_bytes();
better to take it once for each pool where we add entropy.

Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
---
 drivers/char/random.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 391b05a..9564144 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -711,10 +711,15 @@ void add_device_randomness(const void *buf, unsigned int size)
 	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);
 
-- 
1.7.12.rc0.22.gcdd159b

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