Re: [PATCH] driver-core: Log the BUG() causing driver
On 07.03.2018 16:13, Greg Kroah-Hartman wrote: > On Wed, Mar 07, 2018 at 10:49:02AM +0100, Florian Schmaus wrote: >> I triggerd the BUG_ON(), which was added in >> f48f3febb2cbfd0f2ecee7690835ba745c1034a4, when booting a domU Xen >> domain. > > How? Basically just by booting the domU kernel with the wmi-bmof driver compiled in. After I deselected the wmi-bmof driver, the kernel booted just fine. I'd probably be able to re-create the faulty kernel and show you the image and/or kernel config if you want. >> Since there was no contextual information logged, I needed to >> attach kgdb to determine the culprit (the wmi-bmof driver in my case). >> >> 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..55f8db41df2b 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); >> +BUG(); >> +} > > We could just log the error and return with an error, that would be > nicer, right? Crashing the system isn't usually a good idea, even at > boot time :) It sure is, and I did consider it. I just wasn't sure which return value to use in that case. Probably the best solution would be to use the return value of bus_register(), which caused p to become NULL. Although that possibly requires extending the bus_type struct by an 'int' storing the return value (Or could the return value be mangled into the 'p' pointer?). I'd be happy to hear your thoughts on this. BTW: Should I retain the 'unlikely' semantic of BUG_ON() in this case? - Florian signature.asc Description: OpenPGP digital signature
Re: [PATCH] driver-core: Log the BUG() causing driver
On 07.03.2018 16:13, Greg Kroah-Hartman wrote: > On Wed, Mar 07, 2018 at 10:49:02AM +0100, Florian Schmaus wrote: >> I triggerd the BUG_ON(), which was added in >> f48f3febb2cbfd0f2ecee7690835ba745c1034a4, when booting a domU Xen >> domain. > > How? Basically just by booting the domU kernel with the wmi-bmof driver compiled in. After I deselected the wmi-bmof driver, the kernel booted just fine. I'd probably be able to re-create the faulty kernel and show you the image and/or kernel config if you want. >> Since there was no contextual information logged, I needed to >> attach kgdb to determine the culprit (the wmi-bmof driver in my case). >> >> 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..55f8db41df2b 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); >> +BUG(); >> +} > > We could just log the error and return with an error, that would be > nicer, right? Crashing the system isn't usually a good idea, even at > boot time :) It sure is, and I did consider it. I just wasn't sure which return value to use in that case. Probably the best solution would be to use the return value of bus_register(), which caused p to become NULL. Although that possibly requires extending the bus_type struct by an 'int' storing the return value (Or could the return value be mangled into the 'p' pointer?). I'd be happy to hear your thoughts on this. BTW: Should I retain the 'unlikely' semantic of BUG_ON() in this case? - Florian signature.asc Description: OpenPGP digital signature
Re: [PATCH] driver-core: Log the BUG() causing driver
On Wed, Mar 07, 2018 at 10:49:02AM +0100, Florian Schmaus wrote: > I triggerd the BUG_ON(), which was added in > f48f3febb2cbfd0f2ecee7690835ba745c1034a4, when booting a domU Xen > domain. How? > Since there was no contextual information logged, I needed to > attach kgdb to determine the culprit (the wmi-bmof driver in my case). > > 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..55f8db41df2b 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); > + BUG(); > + } We could just log the error and return with an error, that would be nicer, right? Crashing the system isn't usually a good idea, even at boot time :) thanks, greg k-h
Re: [PATCH] driver-core: Log the BUG() causing driver
On Wed, Mar 07, 2018 at 10:49:02AM +0100, Florian Schmaus wrote: > I triggerd the BUG_ON(), which was added in > f48f3febb2cbfd0f2ecee7690835ba745c1034a4, when booting a domU Xen > domain. How? > Since there was no contextual information logged, I needed to > attach kgdb to determine the culprit (the wmi-bmof driver in my case). > > 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..55f8db41df2b 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); > + BUG(); > + } We could just log the error and return with an error, that would be nicer, right? Crashing the system isn't usually a good idea, even at boot time :) thanks, greg k-h