rework the srp api so it takes an srp_ref struct that the caller provides.

the srp_ref struct is used to track the location of the callers
hazard pointer so later calls to srp_follow and srp_enter already
know what to clear. this in turn means most of the caveats around
using srps go away. specifically, you can now:

- switch cpus while holding an srp ref
  - ie, you can sleep while holding an srp ref
- you can take and release srp refs in any order

the original intent was to simplify use of the api when dealing
with complicated data structures. the caller now no longer has to
track the location of the srp a value was fetched from, the srp_ref
effectively does that for you.

srp lists have been refactored to use srp_refs instead of srpl_iter
structs.

this is in preparation of using srps inside the ART code. ART is a
complicated data structure, and lookups require overlapping holds
of srp references.

ok mpi@ jmatthew@

1 files changed, 13 insertions, 11 deletions

diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index 9a8273114bf..31b6ed0c5c2 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bpf.c,v 1.140 2016/05/10 23:48:07 dlg Exp $	*/
+/*	$OpenBSD: bpf.c,v 1.141 2016/05/18 03:46:03 dlg Exp $	*/
 /*	$NetBSD: bpf.c,v 1.33 1997/02/21 23:59:35 thorpej Exp $	*/
 
 /*
@@ -1134,7 +1134,7 @@ int
 bpf_tap(caddr_t arg, u_char *pkt, u_int pktlen, u_int direction)
 {
 	struct bpf_if *bp = (struct bpf_if *)arg;
-	struct srpl_iter i;
+	struct srp_ref sr;
 	struct bpf_d *d;
 	size_t slen;
 	struct timeval tv;
@@ -1144,20 +1144,21 @@ bpf_tap(caddr_t arg, u_char *pkt, u_int pktlen, u_int direction)
 	if (bp == NULL)
 		return (0);
 
-	SRPL_FOREACH(d, &bp->bif_dlist, &i, bd_next) {
+	SRPL_FOREACH(d, &sr, &bp->bif_dlist, bd_next) {
 		atomic_inc_long(&d->bd_rcount);
 
 		if ((direction & d->bd_dirfilt) != 0)
 			slen = 0;
 		else {
+			struct srp_ref sr;
 			struct bpf_program *bf;
 			struct bpf_insn *fcode = NULL;
 
-			bf = srp_enter(&d->bd_rfilter);
+			bf = srp_enter(&sr, &d->bd_rfilter);
 			if (bf != NULL)
 				fcode = bf->bf_insns;
 			slen = bpf_filter(fcode, pkt, pktlen, pktlen);
-			srp_leave(&d->bd_rfilter, bf);
+			srp_leave(&sr);
 		}
 
 		if (slen > 0) {
@@ -1177,7 +1178,7 @@ bpf_tap(caddr_t arg, u_char *pkt, u_int pktlen, u_int direction)
 				drop = 1;
 		}
 	}
-	SRPL_LEAVE(&i, d);
+	SRPL_LEAVE(&sr);
 
 	return (drop);
 }
@@ -1214,7 +1215,7 @@ _bpf_mtap(caddr_t arg, const struct mbuf *m, u_int direction,
     void (*cpfn)(const void *, void *, size_t))
 {
 	struct bpf_if *bp = (struct bpf_if *)arg;
-	struct srpl_iter i;
+	struct srp_ref sr;
 	struct bpf_d *d;
 	size_t pktlen, slen;
 	const struct mbuf *m0;
@@ -1236,20 +1237,21 @@ _bpf_mtap(caddr_t arg, const struct mbuf *m, u_int direction,
 	for (m0 = m; m0 != NULL; m0 = m0->m_next)
 		pktlen += m0->m_len;
 
-	SRPL_FOREACH(d, &bp->bif_dlist, &i, bd_next) {
+	SRPL_FOREACH(d, &sr, &bp->bif_dlist, bd_next) {
 		atomic_inc_long(&d->bd_rcount);
 
 		if ((direction & d->bd_dirfilt) != 0)
 			slen = 0;
 		else {
+			struct srp_ref bsr;
 			struct bpf_program *bf;
 			struct bpf_insn *fcode = NULL;
 
-			bf = srp_enter(&d->bd_rfilter);
+			bf = srp_enter(&bsr, &d->bd_rfilter);
 			if (bf != NULL)
 				fcode = bf->bf_insns;
 			slen = bpf_mfilter(fcode, m, pktlen);
-			srp_leave(&d->bd_rfilter, bf);
+			srp_leave(&bsr);
 		}
 
 		if (slen > 0) {
@@ -1269,7 +1271,7 @@ _bpf_mtap(caddr_t arg, const struct mbuf *m, u_int direction,
 				drop = 1;
 		}
 	}
-	SRPL_LEAVE(&i, d);
+	SRPL_LEAVE(&sr);
 
 	return (drop);
 }