linux-kernel - Re: [PATCH v1] usb: roles: add lockdep class key to struct usb_role

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Message-ID: <d95fce97-61f5-4a0d-a3c9-52df50bfa820@google.com>
Date: Wed, 14 Aug 2024 21:27:24 -0700
From: Amit Sunil Dhamne <amitsd@...gle.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: heikki.krogerus@...ux.intel.com, badhri@...gle.com,
 linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, kyletso@...gle.com,
 rdbabiera@...gle.com
Subject: Re: [PATCH v1] usb: roles: add lockdep class key to struct
 usb_role_switch


On 8/13/24 9:49 PM, Greg KH wrote:
> On Tue, Aug 13, 2024 at 03:42:11PM -0700, Amit Sunil Dhamne wrote:
>> There can be multiple role switch devices running on a platform. Given
>> that lockdep is not capable of differentiating between locks of
>> different instances, false positive warnings for circular locking are
>> reported. To prevent this, register unique lockdep key for each of the
>> individual instances.
>>
>> Signed-off-by: Amit Sunil Dhamne <amitsd@...gle.com>
>> ---
>>   drivers/usb/roles/class.c | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
>> index d7aa913ceb8a..807a8f18ec20 100644
>> --- a/drivers/usb/roles/class.c
>> +++ b/drivers/usb/roles/class.c
>> @@ -11,6 +11,7 @@
>>   #include <linux/usb/role.h>
>>   #include <linux/property.h>
>>   #include <linux/device.h>
>> +#include <linux/lockdep.h>
>>   #include <linux/module.h>
>>   #include <linux/mutex.h>
>>   #include <linux/slab.h>
>> @@ -33,6 +34,10 @@ struct usb_role_switch {
>>   	usb_role_switch_set_t set;
>>   	usb_role_switch_get_t get;
>>   	bool allow_userspace_control;
>> +
>> +#ifdef CONFIG_LOCKDEP
>> +	struct lock_class_key key;
>> +#endif
> Please do not put #ifdef lines in .c files, they are not needed for this
> change to work properly, right?
That's right. I will correct it in the next revision.
>
> checkpatch should have complained about this...

Unfortunately it didn't complain.

Thanks,

Amit

>
> thanks,
>
> greg k-h