Re: Bug in mutex_owned() ?

[Hans Petter Selasky <hselasky%c2i.net@localhost>]

On Sunday 25 October 2009 14:24:47 Mindaugas Rasiukevicius wrote:
> Hans Petter Selasky <hselasky%c2i.net@localhost> wrote:
> > I've currently defined a spinlock type of mutex and my I4B driver code
> > repeatedly crashes due to the fact that mutex_owned() returnes that the
> > mutex is owned while it is actually not. It looks like a bug to me that
> > mutex_owned() always returns (1) in the non-adaptive case!
>
> That is not a bug.  Please see "FULL" definition.  Perhaps you are using
> it not for diagnostic purposes?  In such case, it is wrong.
>
> >   830 #ifdef FULL
> >   831         return __SIMPLELOCK_LOCKED_P(&mtx->mtx_lock);
> >   832 #else
> >   833         return 1;
> >   834 #endif
> >   835 }

A quick search at fxr.watson.org reveals the following for amd64:

   39 static __inline int
   40 __SIMPLELOCK_LOCKED_P(__cpu_simple_lock_t *__ptr)
   41 {
   42         return *__ptr == __SIMPLELOCK_LOCKED;
   43 }

   72 #define __SIMPLELOCK_LOCKED     1
   73 #define __SIMPLELOCK_UNLOCKED   0

mutex_owned() == 1 for spin locks ???

--HPS