expire: Rename ExpKill's EXP_expire to EXP_Inspect

And while at it document it.

bin/varnishd/cache/cache_expire.c

@@ -328,7 +328,7 @@ exp_expire(struct exp_priv *ep, vtim_real now)
 	oc = VBH_root(ep->heap);
 	if (oc == NULL)
 		return (now + 355. / 113.);
-	VSLb(&ep->vsl, SLT_ExpKill, "EXP_expire p=%p e=%.6f f=0x%x", oc,
+	VSLb(&ep->vsl, SLT_ExpKill, "EXP_Inspect p=%p e=%.6f f=0x%x", oc,
 	    oc->timer_when - now, oc->flags);
 
 	CHECK_OBJ_NOTNULL(oc, OBJCORE_MAGIC);

bin/varnishtest/tests/b00063.vtc

@@ -47,9 +47,9 @@ varnish v1 -vcl+backend {
 } -start
 
 logexpect l1 -v v1 -g raw {
-	expect * *	ExpKill		EXP_expire
+	expect * *	ExpKill		EXP_Inspect
 	expect * *	ExpKill		EXP_When
-	expect * *	ExpKill		EXP_expire
+	expect * *	ExpKill		EXP_Inspect
 } -start
 
 client c1 {

bin/varnishtest/tests/c00105.vtc

@@ -35,7 +35,7 @@ varnish v1 -vcl+backend {
 	}
 } -start
 
-logexpect l1 -v v1 -g raw -q "ExpKill ~ EXP_expire" {
+logexpect l1 -v v1 -g raw -q "ExpKill ~ EXP_Inspect" {
 	expect 0 0 ExpKill
 } -start
 

include/tbl/vsl_tags.h

@@ -353,6 +353,9 @@ SLTM(ExpKill, 0, "Object expiry event",
 	"\tLogged when the expiry thread kills an object from the inbox.\n\n"
 	"EXP_When\n"
 	"\tLogged when the expiry thread moves an object on the binheap.\n\n"
+	"EXP_Inspect\n"
+	"\tLogged when the expiry thread inspects the next object scheduled"
+	" to expire.\n\n"
 	"EXP_Expired\n"
 	"\tLogged when the expiry thread expires an object.\n\n"
 	"EXP_Removed\n"
@@ -369,6 +372,7 @@ SLTM(ExpKill, 0, "Object expiry event",
 	"\tEXP_Inbox p=%p e=%f f=0x%x\n"
 	"\tEXP_Kill p=%p e=%f f=0x%x\n"
 	"\tEXP_When p=%p e=%f f=0x%x\n"
+	"\tEXP_Inspect p=%p e=%f f=0x%x\n"
 	"\tEXP_Expired x=%u t=%f h=%u\n"
 	"\tEXP_Removed x=%u t=%f h=%u\n"
 	"\tLRU_Cand p=%p f=0x%x r=%d\n"