linux-kernel - [PATCH 1/1] misc: remove ineffective WARN_ON() check from misc

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Message-ID: <20250827024201.21407-2-xion.wang@mediatek.com>
Date: Wed, 27 Aug 2025 10:41:00 +0800
From: <xion.wang@...iatek.com>
To: Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
CC: <wsd_upstream@...iatek.com>, <huadian.liu@...iatek.com>, Xion Wang
	<xion.wang@...iatek.com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>
Subject: [PATCH 1/1] misc: remove ineffective WARN_ON() check from misc_deregister()

From: Xion Wang <xion.wang@...iatek.com>

The WARN_ON(list_empty(&misc->list)) in misc_deregister() does
not catch any practical error conditions:
- For statically allocated miscdevice structures, the list pointers
 are zero-initialized, so list_empty() returns false, not true.
- After list_del(), the pointers are set to LIST_POISON1 and LIST_POISON2,
 so repeated deregistration also fails to trigger the check.

Signed-off-by: Xion Wang <xion.wang@...iatek.com>
---
 drivers/char/misc.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index 558302a64dd9..f46b00a76a59 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -275,9 +275,6 @@ EXPORT_SYMBOL(misc_register);
 
 void misc_deregister(struct miscdevice *misc)
 {
-	if (WARN_ON(list_empty(&misc->list)))
-		return;
-
 	mutex_lock(&misc_mtx);
 	list_del(&misc->list);
 	device_destroy(&misc_class, MKDEV(MISC_MAJOR, misc->minor));
-- 
2.45.2