panic with em(4) in current

[Giorgos Keramidas]

On Fri, 11 Dec 2009 11:29:45 -0600, Brooks Davis <brooks at freebsd.org> wrote:
> On Fri, Dec 11, 2009 at 01:20:08AM +0300, pluknet wrote:
>> 2009/12/11 Brooks Davis <brooks at one-eyed-alien.net>:
>> > Something with the latest e1000 update in current causes a panic during
>> > attach on my laptop. ?Rolling sys/dev/e1000 back to the previous version
>> > fixes the problem. ?Here's the hand transcribed panic:
>> >
>> > panic: mtx_lock() of spin mutex &dev_spec->swflag_mutex @ ../../../dev/e1000/e1000_ich8lan.c:651
>> >
>> > The back trace places me at: e1000_acquire_swflag_ich8lan()+0x30
>>
>> Hi, I see bug there:
>> +#define E1000_MUTEX_INIT(mutex)         mtx_init((mutex), #mutex, \
>> +                                        MTX_NETWORK_LOCK, \
>> +                                        MTX_DEF | MTX_SPIN)
>>
>> mtx_init() first looks for MTX_SPIN flag and assign
>> lock_class_mtx_spin class to mutex.
>> Then mtx_lock() on spin mutex called.
>
> I can confirm that removing MTX_SPIN fixes the panic.  This is invalid
> code because MTX_DEF and MTX_SPIN are exclusive flags.  Unfortunately,
> MTX_DEF is 0x0 so there's no way to check for that error at runtime.

FWIW, I see the same panic, and will be building a kernel without
MTX_SPIN in a few minutes.

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