[PATCH] random: do not take pool spinlock at boot

[PATCH] random: do not take pool spinlock at boot

[Jason A. Donenfeld]

Since rand_initialize() is run while interrupts are still off and
nothing else is running, we don't need to repeatedly take and release
the pool spinlock, especially in the RDSEED loop.

Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
Dominik - I'm still a bit unclear about early boot semantics that you
seem to know well. Is this patch correct?

 drivers/char/random.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index d4b692c9de68..8088348190e6 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -966,10 +966,10 @@ int __init rand_initialize(void)
 			rv = random_get_entropy();
 			arch_init = false;
 		}
-		mix_pool_bytes(&rv, sizeof(rv));
+		_mix_pool_bytes(&rv, sizeof(rv));
 	}
-	mix_pool_bytes(&now, sizeof(now));
-	mix_pool_bytes(utsname(), sizeof(*(utsname())));
+	_mix_pool_bytes(&now, sizeof(now));
+	_mix_pool_bytes(utsname(), sizeof(*(utsname())));
 
 	extract_entropy(base_crng.key, sizeof(base_crng.key));
 	++base_crng.generation;
-- 
2.35.0

Re: [PATCH] random: do not take pool spinlock at boot

[Dominik Brodowski]

Am Sat, Feb 12, 2022 at 01:28:59AM +0100 schrieb Jason A. Donenfeld:
> Since rand_initialize() is run while interrupts are still off and
> nothing else is running, we don't need to repeatedly take and release
> the pool spinlock, especially in the RDSEED loop.
> 
> Cc: Dominik Brodowski <linux@dominikbrodowski.net>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> Dominik - I'm still a bit unclear about early boot semantics that you
> seem to know well. Is this patch correct?

It seems to be.

	Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>

Thanks,
	Dominik

Re: [PATCH] random: do not take pool spinlock at boot

[Eric Biggers]

On Sat, Feb 12, 2022 at 01:28:59AM +0100, Jason A. Donenfeld wrote:
> Since rand_initialize() is run while interrupts are still off and
> nothing else is running, we don't need to repeatedly take and release
> the pool spinlock, especially in the RDSEED loop.
> 
> Cc: Dominik Brodowski <linux@dominikbrodowski.net>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> Dominik - I'm still a bit unclear about early boot semantics that you
> seem to know well. Is this patch correct?
> 
>  drivers/char/random.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index d4b692c9de68..8088348190e6 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -966,10 +966,10 @@ int __init rand_initialize(void)
>  			rv = random_get_entropy();
>  			arch_init = false;
>  		}
> -		mix_pool_bytes(&rv, sizeof(rv));
> +		_mix_pool_bytes(&rv, sizeof(rv));
>  	}
> -	mix_pool_bytes(&now, sizeof(now));
> -	mix_pool_bytes(utsname(), sizeof(*(utsname())));
> +	_mix_pool_bytes(&now, sizeof(now));
> +	_mix_pool_bytes(utsname(), sizeof(*(utsname())));
>  
>  	extract_entropy(base_crng.key, sizeof(base_crng.key));
>  	++base_crng.generation;
> -- 
> 2.35.0

Reviewed-by: Eric Biggers <ebiggers@google.com>

- Eric