linux-kernel - [PATCH 2/4] hw_random: start and stop in-kernel rngd in separate function

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Date:   Sun, 13 Feb 2022 21:46:29 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        "Jason A . Donenfeld" <Jason@...c4.com>
Subject: [PATCH 2/4] hw_random: start and stop in-kernel rngd in separate function

Extract the start/stop logic for the in-kernel rngd thread to
a separate function.

Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>
---
 drivers/char/hw_random/core.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 6f09f4e5af20..29febf55b0d4 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -51,7 +51,7 @@ MODULE_PARM_DESC(default_quality,
 
 static void drop_current_rng(void);
 static int hwrng_init(struct hwrng *rng);
-static void start_khwrngd(void);
+static void hwrng_manage_rngd(void);
 
 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
 			       int wait);
@@ -164,10 +164,7 @@ static int hwrng_init(struct hwrng *rng)
 	if (current_quality > 1024)
 		current_quality = 1024;
 
-	if (current_quality == 0 && hwrng_fill)
-		kthread_stop(hwrng_fill);
-	if (current_quality > 0 && !hwrng_fill)
-		start_khwrngd();
+	hwrng_manage_rngd();
 
 	return 0;
 }
@@ -466,12 +463,19 @@ static int hwrng_fillfn(void *unused)
 	return 0;
 }
 
-static void start_khwrngd(void)
+static void hwrng_manage_rngd(void)
 {
-	hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
-	if (IS_ERR(hwrng_fill)) {
-		pr_err("hwrng_fill thread creation failed\n");
-		hwrng_fill = NULL;
+	if (WARN_ON(!mutex_is_locked(&rng_mutex)))
+		return;
+
+	if (current_quality == 0 && hwrng_fill)
+		kthread_stop(hwrng_fill);
+	if (current_quality > 0 && !hwrng_fill) {
+		hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
+		if (IS_ERR(hwrng_fill)) {
+			pr_err("hwrng_fill thread creation failed\n");
+			hwrng_fill = NULL;
+		}
 	}
 }
 
-- 
2.35.1