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Subject[PATCH] random: reorder READ_ONCE() in get_random_uXX
Date
Since commit 4a072c71f49b ("random: silence compiler warnings and fix
race") there is a READ_ONCE().
I doubt that this required here but I don't have the time to argue with
Jason. Instead I push the access further down so we don't read crng_init
if we can leave the function after arch_get_random_XXX(). This is
something the compiler did before the READ_ONCE() got it.

Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/char/random.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 01a260f67437..5e3765f6a61d 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2041,7 +2041,7 @@ 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;

@@ -2053,6 +2053,7 @@ u64 get_random_u64(void)
arch_get_random_long((unsigned long *)&ret + 1))
return ret;
#endif
+ use_lock = READ_ONCE(crng_init) < 2;

batch = &get_cpu_var(batched_entropy_u64);
if (use_lock)
@@ -2073,13 +2074,14 @@ 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;

if (arch_get_random_int(&ret))
return ret;

+ 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);
--
2.13.2
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