On Tuesday 28 March 2006 13:05, Dag-Erling Smørgrav wrote:
> John Baldwin <[EMAIL PROTECTED]> writes:
> > One reason for not having the casts, btw, is that you lose type
> > checking.
>
> Huh? Before my patch, any use of atomic_*_ptr with warnings turned
> off would result in a slew of warnings because you'd be passing
> pointers to a function which is declared to take u_int. The only way
> to make this type safe is to use inline functions instead of the
> macros I wrote.
s/off/on/ I trust
Not true. The tinderbox would attest to that. Please see code such as
this:
#define MTX_UNOWNED 0x00000004 /* Cookie for free mutex */
...
/* Try to obtain mtx_lock once. */
#ifndef _obtain_lock
#define _obtain_lock(mp, tid) \
atomic_cmpset_acq_ptr(&(mp)->mtx_lock, MTX_UNOWNED, (tid))
#endif
...
void
_mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file,
int line)
{
...
uintptr_t v;
...
while (!_obtain_lock(m, tid)) {
...
v = m->mtx_lock;
...
/*
* If the mutex isn't already contested and a failure occurs
* setting the contested bit, the mutex was either released
* or the state of the MTX_RECURSED bit changed.
*/
if ((v & MTX_CONTESTED) == 0 &&
!atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
...
continue;
}
...
}
...
}
etc. kern_rwlock.c has this as well. The parts of the kernel that
do use pointers already use explicit casts to uintptr_t where needed:
dev/hatm/if_hatm_intr.c: if (atomic_cmpset_ptr((uintptr_t
*)list, (uintptr_t)buf->link,
dev/hatm/if_hatm_intr.c: if (atomic_cmpset_ptr((uintptr_t
*)&sc->mbuf_list[g],
dev/hatm/if_hatm_intr.c: if
(atomic_cmpset_ptr((uintptr_t *)&sc->mbuf_list[g],
Even userland uses casts when it uses void * rather than uintptr_t for
the underlying type. See src/lib/libpthread/sys/lock.c or
src/lib/libthr/thr_umtx.h.
--
John Baldwin <[EMAIL PROTECTED]> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
_______________________________________________
[email protected] mailing list
http://lists.freebsd.org/mailman/listinfo/cvs-all
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
