Date: Wed, 14 Apr 2004 15:04:53 -0700 (PDT) From: wpaul@FreeBSD.ORG (Bill Paul) To: jhb@FreeBSD.org (John Baldwin) Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/compat/ndis hal_var.h kern_ndis.c ndis_var.h ntoskrnl_var.h pe_var.h subr_hal.c subr_ndis.c subr_ntoskrn Message-ID: <20040414220453.7806316A4CF@hub.freebsd.org> In-Reply-To: <200404141105.43663.jhb@FreeBSD.org> from John Baldwin at "Apr 14, 2004 11:05:43 am"
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> > Now, I'm sure many people will be seized by the urge to criticize
> > me for doing an end run around our own spinlock implementation, but
> > it makes more sense to do it this way. Well, it does to me anyway.
>
> If you don't use atomic ops with memory barriers somewhere (like the mutex
> implementation does) then NDIS won't work on SMP. Really, IRQL is basically
> spl()s, and we don't use an spl-like model anymore. Just using mutexes for
> locking should give you all the protection you need.
Protection is all well and good, but I need to provide the right semantics
as well. I need to fool the drivers into thinking they can depend on the
usual Windows behavior, and make it easy to use the Windows data types,
and it's a pain in the butt to do that with regular mutexes.
And besides, I wanna.
Now, from subr_ntoskrnl.c:
__stdcall void
ntoskrnl_lock_dpc(/*lock*/ void)
{
kspin_lock *lock;
__asm__ __volatile__ ("" : "=c" (lock));
while (atomic_cmpset_int((volatile u_int *)lock, 0, 1) == 0)
/* do nothing */;
return;
}
__stdcall void
ntoskrnl_unlock_dpc(/*lock*/ void)
{
kspin_lock *lock;
__asm__ __volatile__ ("" : "=c" (lock));
atomic_cmpset_int((volatile u_int *)lock, 1, 0);
return;
}
These two routines do the actual work of acquiring and releasing the
lock (they map to KefAcquireSpinLockAtDpcLevel() and
KefReleaseSpinLockFromDpcLevel). Are you saying the former routine
should use atomic_cmpset_acq_int() and the latter atomic_cmpset_rel_int()?
-Bill
--
=============================================================================
-Bill Paul (510) 749-2329 | Senior Engineer, Master of Unix-Fu
wpaul@windriver.com | Wind River Systems
=============================================================================
<adamw> you're just BEGGING to face the moose
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