linux-kernel - [PATCH] hw_random: don't wait on add_early

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Date:   Tue, 17 Sep 2019 11:54:50 +0200
From:   Laurent Vivier <lvivier@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Amit Shah <amit@...nel.org>, linux-crypto@...r.kernel.org,
        Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Laurent Vivier <lvivier@...hat.com>
Subject: [PATCH] hw_random: don't wait on add_early_randomness()

add_early_randomness() is called by hwrng_register() when the
hardware is added. If this hardware and its module are present
at boot, and if there is no data available the boot hangs until
data are available and can't be interrupted.

To avoid that, call rng_get_data() in non-blocking mode (wait=0)
from add_early_randomness().

Signed-off-by: Laurent Vivier <lvivier@...hat.com>
---
 drivers/char/hw_random/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 9044d31ab1a1..8d53b8ef545c 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -67,7 +67,7 @@ static void add_early_randomness(struct hwrng *rng)
 	size_t size = min_t(size_t, 16, rng_buffer_size());
 
 	mutex_lock(&reading_mutex);
-	bytes_read = rng_get_data(rng, rng_buffer, size, 1);
+	bytes_read = rng_get_data(rng, rng_buffer, size, 0);
 	mutex_unlock(&reading_mutex);
 	if (bytes_read > 0)
 		add_device_randomness(rng_buffer, bytes_read);
-- 
2.21.0