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

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Date:   Sat, 12 Feb 2022 01:28:59 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux@...inikbrodowski.net, linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] random: do not take pool spinlock at boot

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@...inikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.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