From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 4 May 2018 10:38:50 -0700 From: Greg Kroah-Hartman To: Florian Schmaus Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] driver-core: Return EBUSY error instead of BUG_ON() Message-ID: <20180504173850.GD4649@kroah.com> References: <20180307094902.20316-1-flo@geekplace.eu> <20180504132357.31771-1-flo@geekplace.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180504132357.31771-1-flo@geekplace.eu> User-Agent: Mutt/1.9.5 (2018-04-13) X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Fri, May 04, 2018 at 03:23:57PM +0200, Florian Schmaus wrote: > 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 > --- > 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; > + } In looking at this code, that's a real bug somewhere in the logic of the bus subsystem. BUG_ON() is a pretty big hammer, I agree, but your error message should be a lot more descriptive, and the error value should not be BUSY, as something went wrong, it's not just a "come back later" type of thing. thanks, greg k-h