Author: markj
Date: Tue Sep 15 19:21:58 2020
New Revision: 365760
URL: https://svnweb.freebsd.org/changeset/base/365760
Log:
Improve unix socket PCB refcounting.
- Use refcount_init().
- Define an INVARIANTS-only zone destructor to assert that various
bits of PCB state aren't left dangling.
- Annotate unp_pcb_rele() with __result_use_check.
- Simplify control flow.
Reviewed by: glebius, kevans, kib
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26295
Modified:
head/sys/kern/uipc_usrreq.c
Modified: head/sys/kern/uipc_usrreq.c
==============================================================================
--- head/sys/kern/uipc_usrreq.c Tue Sep 15 19:21:33 2020 (r365759)
+++ head/sys/kern/uipc_usrreq.c Tue Sep 15 19:21:58 2020 (r365760)
@@ -313,25 +313,25 @@ static void unp_process_defers(void * __unused,
int);
static void
unp_pcb_hold(struct unpcb *unp)
{
- MPASS(unp->unp_refcount);
- refcount_acquire(&unp->unp_refcount);
+ u_int old __unused;
+
+ old = refcount_acquire(&unp->unp_refcount);
+ KASSERT(old > 0, ("%s: unpcb %p has no references", __func__, unp));
}
-static int
+static __result_use_check bool
unp_pcb_rele(struct unpcb *unp)
{
- int freed;
+ bool ret;
UNP_PCB_LOCK_ASSERT(unp);
- MPASS(unp->unp_refcount);
- if ((freed = refcount_release(&unp->unp_refcount))) {
- /* we got here with having detached? */
- MPASS(unp->unp_socket == NULL);
+
+ if ((ret = refcount_release(&unp->unp_refcount))) {
UNP_PCB_UNLOCK(unp);
UNP_PCB_LOCK_DESTROY(unp);
uma_zfree(unp_zone, unp);
}
- return (freed);
+ return (ret);
}
static void
@@ -514,7 +514,7 @@ uipc_attach(struct socket *so, int proto, struct threa
UNP_PCB_LOCK_INIT(unp);
unp->unp_socket = so;
so->so_pcb = unp;
- unp->unp_refcount = 1;
+ refcount_init(&unp->unp_refcount, 1);
if ((locked = UNP_LINK_WOWNED()) == false)
UNP_LINK_WLOCK();
@@ -1814,7 +1814,7 @@ unp_pcblist(SYSCTL_HANDLER_ARGS)
struct unp_head *head;
struct xunpcb *xu;
u_int i;
- int error, freeunp, n;
+ int error, n;
switch ((intptr_t)arg1) {
case SOCK_STREAM:
@@ -1891,9 +1891,10 @@ unp_pcblist(SYSCTL_HANDLER_ARGS)
for (i = 0; i < n; i++) {
unp = unp_list[i];
UNP_PCB_LOCK(unp);
- freeunp = unp_pcb_rele(unp);
+ if (unp_pcb_rele(unp))
+ continue;
- if (freeunp == 0 && unp->unp_gencnt <= gencnt) {
+ if (unp->unp_gencnt <= gencnt) {
xu->xu_len = sizeof *xu;
xu->xu_unpp = (uintptr_t)unp;
/*
@@ -1920,8 +1921,9 @@ unp_pcblist(SYSCTL_HANDLER_ARGS)
sotoxsocket(unp->unp_socket, &xu->xu_socket);
UNP_PCB_UNLOCK(unp);
error = SYSCTL_OUT(req, xu, sizeof *xu);
- } else if (freeunp == 0)
+ } else {
UNP_PCB_UNLOCK(unp);
+ }
}
free(xu, M_TEMP);
if (!error) {
@@ -2137,18 +2139,44 @@ unp_zone_change(void *tag)
uma_zone_set_max(unp_zone, maxsockets);
}
+#ifdef INVARIANTS
static void
+unp_zdtor(void *mem, int size __unused, void *arg __unused)
+{
+ struct unpcb *unp;
+
+ unp = mem;
+
+ KASSERT(LIST_EMPTY(&unp->unp_refs),
+ ("%s: unpcb %p has lingering refs", __func__, unp));
+ KASSERT(unp->unp_socket == NULL,
+ ("%s: unpcb %p has socket backpointer", __func__, unp));
+ KASSERT(unp->unp_vnode == NULL,
+ ("%s: unpcb %p has vnode references", __func__, unp));
+ KASSERT(unp->unp_conn == NULL,
+ ("%s: unpcb %p is still connected", __func__, unp));
+ KASSERT(unp->unp_addr == NULL,
+ ("%s: unpcb %p has leaked addr", __func__, unp));
+}
+#endif
+
+static void
unp_init(void)
{
+ uma_dtor dtor;
#ifdef VIMAGE
if (!IS_DEFAULT_VNET(curvnet))
return;
#endif
- unp_zone = uma_zcreate("unpcb", sizeof(struct unpcb), NULL, NULL,
+
+#ifdef INVARIANTS
+ dtor = unp_zdtor;
+#else
+ dtor = NULL;
+#endif
+ unp_zone = uma_zcreate("unpcb", sizeof(struct unpcb), NULL, dtor,
NULL, NULL, UMA_ALIGN_CACHE, 0);
- if (unp_zone == NULL)
- panic("unp_init");
uma_zone_set_max(unp_zone, maxsockets);
uma_zone_set_warning(unp_zone, "kern.ipc.maxsockets limit reached");
EVENTHANDLER_REGISTER(maxsockets_change, unp_zone_change,
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