hash: Avoid locking objhead twice to withdraw

varnishcache · Jan 29, 2024 · ea4ba6f · ea4ba6f
1 parent e918ee6
commit ea4ba6f
Show file tree

Hide file tree

Showing 2 changed files with 20 additions and 5 deletions.
diff --git a/bin/varnishd/cache/cache_hash.c b/bin/varnishd/cache/cache_hash.c
@@ -954,11 +954,10 @@ HSH_Withdraw(struct worker *wrk, struct objcore **ocp)
 	assert(oh->refcnt > 0);
 	oc->flags = OC_F_WITHDRAW;
 	hsh_rush1(wrk, oc, &rush);
-	Lck_Unlock(&oh->mtx);
+	AZ(HSH_DerefObjCoreUnlock(wrk, &oc));
 
 	hsh_rush2(wrk, &rush);
 
-	AZ(HSH_DerefObjCore(wrk, &oc));
 }
 
 /*---------------------------------------------------------------------
@@ -1145,18 +1144,33 @@ HSH_DerefObjCore(struct worker *wrk, struct objcore **ocp)
 {
 	struct objcore *oc;
 	struct objhead *oh;
-	struct rush rush;
-	int r;
 
 	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
 	TAKE_OBJ_NOTNULL(oc, ocp, OBJCORE_MAGIC);
 	assert(oc->refcnt > 0);
-	INIT_OBJ(&rush, RUSH_MAGIC);
 
 	oh = oc->objhead;
 	CHECK_OBJ_NOTNULL(oh, OBJHEAD_MAGIC);
 
 	Lck_Lock(&oh->mtx);
+	return (HSH_DerefObjCoreUnlock(wrk, &oc));
+}
+
+int
+HSH_DerefObjCoreUnlock(struct worker *wrk, struct objcore **ocp)
+{
+	struct objcore *oc;
+	struct objhead *oh;
+	int r;
+
+	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
+	TAKE_OBJ_NOTNULL(oc, ocp, OBJCORE_MAGIC);
+	assert(oc->refcnt > 0);
+
+	oh = oc->objhead;
+	CHECK_OBJ_NOTNULL(oh, OBJHEAD_MAGIC);
+
+	Lck_AssertHeld(&oh->mtx);
 	assert(oh->refcnt > 0);
 	r = --oc->refcnt;
 	if (!r)

diff --git a/bin/varnishd/cache/cache_objhead.h b/bin/varnishd/cache/cache_objhead.h
@@ -76,6 +76,7 @@ struct boc *HSH_RefBoc(const struct objcore *);
 void HSH_DerefBoc(struct worker *wrk, struct objcore *);
 void HSH_DeleteObjHead(const struct worker *, struct objhead *);
 int HSH_DerefObjCore(struct worker *, struct objcore **);
+int HSH_DerefObjCoreUnlock(struct worker *, struct objcore **);
 enum lookup_e HSH_Lookup(struct req *, struct objcore **, struct objcore **);
 void HSH_Ref(struct objcore *o);
 void HSH_AddString(struct req *, void *ctx, const char *str);