linux-kernel - [PATCH v2] driver-core: Return EBUSY error instead of BUG

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Date:   Fri,  4 May 2018 15:23:57 +0200
From:   Florian Schmaus <flo@...kplace.eu>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, Florian Schmaus <flo@...kplace.eu>
Subject: [PATCH v2] driver-core: Return EBUSY error instead of BUG_ON()

I triggerd the BUG_ON() in driver_register(), which was added in
f48f3febb2cbfd0f2ecee7690835ba745c1034a4, when booting a domU Xen
domain. Since there was no contextual information logged, I needed to
attach kgdb to determine the culprit (the wmi-bmof driver in my case).

Instead of running into a BUG_ON() we print an error message
identifying the driver but continue booting.

Signed-off-by: Florian Schmaus <flo@...kplace.eu>
---
 drivers/base/driver.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/base/driver.c b/drivers/base/driver.c
index ba912558a510..63baec586eba 100644
--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -148,7 +148,11 @@ int driver_register(struct device_driver *drv)
 	int ret;
 	struct device_driver *other;
 
-	BUG_ON(!drv->bus->p);
+	if (!drv->bus->p) {
+		printk(KERN_ERR "Driver '%s' was unable to register bus_type\n",
+			   drv->name);
+		return -EBUSY;
+	}
 
 	if ((drv->bus->probe && drv->probe) ||
 	    (drv->bus->remove && drv->remove) ||
-- 
2.16.1