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Date:      Sat, 06 Sep 2008 23:27:09 -0700
From:      Julian Elischer <julian@elischer.org>
To:        Marko Zec <zec@FreeBSD.org>, FreeBSD virtualization mailing list <freebsd-virtualization@freebsd.org>
Subject:   FOREACH_VNET...
Message-ID:  <48C3743D.9090503@elischer.org>
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trying to replace VNET_ITERLOOP_{BEGIN,END}



looking at an example:

static void
if_slowtimo(void *arg)
{
         struct ifnet *ifp;

         IFNET_RLOCK();
         VNET_ITERLOOP_BEGIN();
         INIT_VNET_NET(curvnet);
         TAILQ_FOREACH(ifp, &V_ifnet, if_link) {
                 if (ifp->if_timer == 0 || --ifp->if_timer)
                         continue;
                 if (ifp->if_watchdog)
                         (*ifp->if_watchdog)(ifp);
         }
         VNET_ITERLOOP_END();
         IFNET_RUNLOCK();
         timeout(if_slowtimo, (void *)0, hz / IFNET_SLOWHZ);
}


If we expand this out we get: (reindented for readability)

static void
if_slowtimo(void *arg)
{
         struct ifnet *ifp;

         IFNET_RLOCK();
         struct vnet *vnet_iter;
         VNET_LIST_REF();
         LIST_FOREACH(vnet_iter, &vnet_head, vnet_le) {
                 struct vnet *saved_vnet = curvnet;
                 curvnet = vnet_iter;
                 INIT_VNET_NET(curvnet);
                 TAILQ_FOREACH(ifp, &V_ifnet, if_link) {
                         if (ifp->if_timer == 0 || --ifp->if_timer)
                                 continue;
                         if (ifp->if_watchdog)
                                 (*ifp->if_watchdog)(ifp);
                 }
                 curvnet = saved_vnet;
         }
         VNET_LIST_UNREF();
         IFNET_RUNLOCK();
         timeout(if_slowtimo, (void *)0, hz / IFNET_SLOWHZ);
}

now several things leap out here..
(like, declaring variables in mid block)
using different macros to try do this cleanly might lead to:



static void
if_slowtimo(void *arg)
{
         struct ifnet *ifp;
         VNET_DECL(vnet_iter);
         VNET_DECL(saved_vnet);

         IFNET_RLOCK();
	CURVNET_SAVE(saved_vnet);
         VNET_LIST_REF();
         FOREACH_VNET(vnet_iter) {
		
                 CURVNET_SET_QUIET(vnet_iter);
                 INIT_VNET_NET(vnet_iter);
                 TAILQ_FOREACH(ifp, &V_ifnet, if_link) {
                         if (ifp->if_timer == 0 || --ifp->if_timer)
                                 continue;
                         if (ifp->if_watchdog)
                                 (*ifp->if_watchdog)(ifp);
                 }
         }
         CURVNET_SET(vnet_hold);
         VNET_LIST_UNREF();
         IFNET_RUNLOCK();
         timeout(if_slowtimo, (void *)0, hz / IFNET_SLOWHZ);
}

this adds a lot to the original..

I could see:

using bigger macros, getting it back (size wise) to:

static void
if_slowtimo(void *arg)
{
         struct ifnet *ifp;
         VNET_ITERATOR_DECL(vnet_iter, saved_vnet);

         IFNET_RLOCK();
         FOREACH_VNET(vnet_iter, saved_vnet) {
		VNET_SWITCHTO(vnet_iter);
                 TAILQ_FOREACH(ifp, &V_ifnet, if_link) {
                         if (ifp->if_timer == 0 || --ifp->if_timer)
                                 continue;
                         if (ifp->if_watchdog)
                                 (*ifp->if_watchdog)(ifp);
                 }
         }
         FOREACH_VNET_COMPLETE(saved_vnet);
         IFNET_RUNLOCK();
         timeout(if_slowtimo, (void *)0, hz / IFNET_SLOWHZ);
}

still bigger than the original macros though arguably more "C-like"

anyone have better ways to express this?

Brook, robert, bz? does this look better?


Julian

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