linux-kernel - Re: [PATCH] reset: Further simplify locking with guard()

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Message-ID: <b050730e-ac7d-401b-8210-82453d05b0e5@web.de>
Date: Sun, 29 Sep 2024 12:45:27 +0200
From: Markus Elfring <Markus.Elfring@....de>
To: Philipp Zabel <p.zabel@...gutronix.de>, kernel@...gutronix.de,
 linux-arm-kernel@...ts.infradead.org,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: LKML <linux-kernel@...r.kernel.org>, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] reset: Further simplify locking with guard()

> Use guard(mutex) to automatically unlock mutexes when going out of
> scope. Simplify error paths by removing a goto and manual mutex
> unlocking in multiple places.
…
> +++ b/drivers/reset/core.c
…
@@ -1041,29 +1036,27 @@ __of_reset_control_get(struct device_node *node, const char *id, int index,
 		}
 	}

-	mutex_lock(&reset_list_mutex);
+	guard(mutex)(&reset_list_mutex);
 	rcdev = __reset_find_rcdev(&args, gpio_fallback);
…
 	rstc = __reset_control_get_internal(rcdev, rstc_id, shared, acquired);

-out_unlock:
-	mutex_unlock(&reset_list_mutex);
 out_put:
 	of_node_put(args.np);
…

Would you like to preserve the same lock scope (which ended before this function call)?


@@ -1098,7 +1091,7 @@ __reset_control_get_from_lookup(struct device *dev, const char *con_id,
 	const char *dev_id = dev_name(dev);
 	struct reset_control *rstc = NULL;

-	mutex_lock(&reset_lookup_mutex);
+	guard(mutex)(&reset_lookup_mutex);

 	list_for_each_entry(lookup, &reset_lookup_list, list) {
…
 			break;
 		}
 	}

-	mutex_unlock(&reset_lookup_mutex);
-
 	if (!rstc)
 		return optional ? NULL : ERR_PTR(-ENOENT);
…

Would you really like to increase the lock scope here?

Regards,
Markus