random: reorder READ_ONCE() in get_random_uXX

Sebastian Andrzej Siewior · tytso · commit 72e5c740f633 · 2017-07-15T12:33:22.000-04:00
Avoid the READ_ONCE in commit 4a072c7 ("random: silence compiler warnings and fix race") if we can leave the function after arch_get_random_XXX(). Cc: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/drivers/char/random.c b/drivers/char/random.c
@@ -2089,7 +2089,7 @@ static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64);
 u64 get_random_u64(void)
 {
 	u64 ret;
-	bool use_lock = READ_ONCE(crng_init) < 2;
+	bool use_lock;
 	unsigned long flags = 0;
 	struct batched_entropy *batch;
 	static void *previous;
@@ -2105,6 +2105,7 @@ u64 get_random_u64(void)
 
 	warn_unseeded_randomness(&previous);
 
+	use_lock = READ_ONCE(crng_init) < 2;
 	batch = &get_cpu_var(batched_entropy_u64);
 	if (use_lock)
 		read_lock_irqsave(&batched_entropy_reset_lock, flags);
@@ -2124,7 +2125,7 @@ static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32);
 u32 get_random_u32(void)
 {
 	u32 ret;
-	bool use_lock = READ_ONCE(crng_init) < 2;
+	bool use_lock;
 	unsigned long flags = 0;
 	struct batched_entropy *batch;
 	static void *previous;
@@ -2134,6 +2135,7 @@ u32 get_random_u32(void)
 
 	warn_unseeded_randomness(&previous);
 
+	use_lock = READ_ONCE(crng_init) < 2;
 	batch = &get_cpu_var(batched_entropy_u32);
 	if (use_lock)
 		read_lock_irqsave(&batched_entropy_reset_lock, flags);
