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Improve unix socket PCB refcounting.

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- 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
This commit is contained in:
Mark Johnston 2020-09-15 19:21:58 +00:00
parent d5cbccecd8
commit 5362170da7
1 changed files with 45 additions and 17 deletions
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62
sys/kern/uipc_usrreq.c
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@ -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 thread *td)
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,