Re: ixg(4) mutex problem (PR#49328)

[Chuck Silvers <chuq%chuq.com@localhost>]

On Thu, Jan 29, 2015 at 04:31:27PM +0900, Masanobu SAITOH wrote:
>  Hi.
> 
> ?Uwe Toenjes found a bug in ixg(4). See:
> 
> 	http://mail-index.netbsd.org/current-users/2014/10/11/msg025932.html
> 
> Then, PR#49328 was submitted by him.
> 
> 	http://gnats.netbsd.org/49328
> 
> This problem is can be reproduced when
> 
> 	LOCKDEBUG is defined
> 	ifconfig ixg0 up
> 
> ixg(4) take a spin mutex before accessing MAC core:
> 
> ------ ixgbe.h -------
> #define IXGBE_CORE_LOCK_INIT(_sc, _name) \
>         mutex_init(&(_sc)->core_mtx, MUTEX_DEFAULT, IPL_NET)


in freebsd, this mutex is not a spin mutex:

#define IXGBE_CORE_LOCK_INIT(_sc, _name) \
        mtx_init(&(_sc)->core_mtx, _name, "IXGBE Core Lock", MTX_DEF)

#define MTX_DEF         0x00000000      /* DEFAULT (sleep) lock */
#define MTX_SPIN        0x00000001      /* Spin lock (disables interrupts) */


I'm not familiar enough with the current state or planned future direction
of our network stack to say which way makes more sense for us.

-Chuck