diff --git a/CHANGES b/CHANGES
index 3ee9755dbc..6d2b6f1138 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,7 @@
+3860.	[bug]		ioctl(DP_POLL) array size needs to be determined
+			at run time as it is limited to {OPEN_MAX}.
+			[RT #35878]
+
 3858.	[bug]		Disable GCC 4.9 "delete null pointer check".
 			[RT #35968]
 
diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index 0dd5bbce5e..c6c02ae270 100644
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -58,6 +58,7 @@
 #include <isc/platform.h>
 #include <isc/print.h>
 #include <isc/region.h>
+#include <isc/resource.h>
 #include <isc/socket.h>
 #include <isc/stats.h>
 #include <isc/strerror.h>
@@ -402,6 +403,8 @@ struct isc__socketmgr {
 #endif	/* USE_EPOLL */
 #ifdef USE_DEVPOLL
 	int			devpoll_fd;
+	isc_resourcevalue_t	open_max;
+	unsigned int		calls;
 	int			nevents;
 	struct pollfd		*events;
 #endif	/* USE_DEVPOLL */
@@ -1168,8 +1171,6 @@ select_readmsg(isc__socketmgr_t *mgr, int *fd, int *msg) {
 					   "read() failed "
 					   "during watcher poke: %s"),
 			    strbuf);
-
-		return;
 	}
 	INSIST(cc == sizeof(buf));
 
@@ -4098,8 +4099,10 @@ watcher(void *uap) {
 #elif defined (USE_EPOLL)
 	const char *fnname = "epoll_wait()";
 #elif defined(USE_DEVPOLL)
+	isc_result_t result;
 	const char *fnname = "ioctl(DP_POLL)";
 	struct dvpoll dvp;
+	int pass;
 #elif defined (USE_SELECT)
 	const char *fnname = "select()";
 	int maxfd;
@@ -4126,17 +4129,45 @@ watcher(void *uap) {
 			cc = epoll_wait(manager->epoll_fd, manager->events,
 					manager->nevents, -1);
 #elif defined(USE_DEVPOLL)
-			dvp.dp_fds = manager->events;
-			dvp.dp_nfds = manager->nevents;
+			/*
+			 * Re-probe every thousand calls.
+			 */
+			if (manager->calls++ > 1000U) {
+				result = isc_resource_getcurlimit(
+							isc_resource_openfiles,
+							&manager->open_max);
+				if (result != ISC_R_SUCCESS)
+					manager->open_max = 64;
+				manager->calls == 0;
+			}
+			for (pass = 0; pass < 2; pass++) {
+				dvp.dp_fds = manager->events;
+				dvp.dp_nfds = manager->nevents;
+				if (dvp.dp_nfds >= manager->open_max)
+					dvp.dp_nfds = manager->open_max - 1;
 #ifndef ISC_SOCKET_USE_POLLWATCH
-			dvp.dp_timeout = -1;
-#else
-			if (pollstate == poll_idle)
 				dvp.dp_timeout = -1;
-			else
-				dvp.dp_timeout = ISC_SOCKET_POLLWATCH_TIMEOUT;
+#else
+				if (pollstate == poll_idle)
+					dvp.dp_timeout = -1;
+				else
+					dvp.dp_timeout =
+						 ISC_SOCKET_POLLWATCH_TIMEOUT;
 #endif	/* ISC_SOCKET_USE_POLLWATCH */
-			cc = ioctl(manager->devpoll_fd, DP_POLL, &dvp);
+				cc = ioctl(manager->devpoll_fd, DP_POLL, &dvp);
+				if (cc == -1 && errno == EINVAL) {
+					/*
+					 * {OPEN_MAX} may have dropped.  Look
+					 * up the current value and try again.
+					 */
+					result = isc_resource_getcurlimit(
+							isc_resource_openfiles,
+							&manager->open_max);
+					if (result != ISC_R_SUCCESS)
+						manager->open_max = 64;
+				} else
+					break;
+			}
 #elif defined(USE_SELECT)
 			LOCK(&manager->lock);
 			memmove(manager->read_fds_copy, manager->read_fds,
@@ -4296,11 +4327,12 @@ setup_watcher(isc_mem_t *mctx, isc__socketmgr_t *manager) {
 	}
 #endif	/* USE_WATCHER_THREAD */
 #elif defined(USE_DEVPOLL)
-	/*
-	 * XXXJT: /dev/poll seems to reject large numbers of events,
-	 * so we should be careful about redefining ISC_SOCKET_MAXEVENTS.
-	 */
 	manager->nevents = ISC_SOCKET_MAXEVENTS;
+	result = isc_resource_getcurlimit(isc_resource_openfiles,
+					  &manager->open_max);
+	if (result != ISC_R_SUCCESS)
+		manager->open_max = 64;
+	manager->calls = 0;
 	manager->events = isc_mem_get(mctx, sizeof(struct pollfd) *
 				      manager->nevents);
 	if (manager->events == NULL)
@@ -6149,8 +6181,6 @@ isc__socketmgr_waitevents(isc_socketmgr_t *manager0, struct timeval *tvp,
 			  isc_socketwait_t **swaitp)
 {
 	isc__socketmgr_t *manager = (isc__socketmgr_t *)manager0;
-
-
 	int n;
 #ifdef USE_KQUEUE
 	struct timespec ts, *tsp;
@@ -6159,6 +6189,8 @@ isc__socketmgr_waitevents(isc_socketmgr_t *manager0, struct timeval *tvp,
 	int timeout;
 #endif
 #ifdef USE_DEVPOLL
+	isc_result_t result;
+	int pass;
 	struct dvpoll dvp;
 #endif
 
@@ -6192,15 +6224,41 @@ isc__socketmgr_waitevents(isc_socketmgr_t *manager0, struct timeval *tvp,
 					   manager->nevents, timeout);
 	n = swait_private.nevents;
 #elif defined(USE_DEVPOLL)
-	dvp.dp_fds = manager->events;
-	dvp.dp_nfds = manager->nevents;
-	if (tvp != NULL) {
-		dvp.dp_timeout = tvp->tv_sec * 1000 +
-			(tvp->tv_usec + 999) / 1000;
-	} else
-		dvp.dp_timeout = -1;
-	swait_private.nevents = ioctl(manager->devpoll_fd, DP_POLL, &dvp);
-	n = swait_private.nevents;
+	/*
+	 * Re-probe every thousand calls.
+	 */
+	if (manager->calls++ > 1000U) {
+		result = isc_resource_getcurlimit(isc_resource_openfiles,
+						  &manager->open_max);
+		if (result != ISC_R_SUCCESS)
+			manager->open_max = 64;
+		manager->calls == 0;
+	}
+	for (pass = 0; pass < 2; pass++) {
+		dvp.dp_fds = manager->events;
+		dvp.dp_nfds = manager->nevents;
+		if (dvp.dp_nfds >= manager->open_max)
+			dvp.dp_nfds = manager->open_max - 1;
+		if (tvp != NULL) {
+			dvp.dp_timeout = tvp->tv_sec * 1000 +
+				(tvp->tv_usec + 999) / 1000;
+		} else
+			dvp.dp_timeout = -1;
+		n = ioctl(manager->devpoll_fd, DP_POLL, &dvp);
+		if (n == -1 && errno == EINVAL) {
+			/*
+			 * {OPEN_MAX} may have dropped.  Look
+			 * up the current value and try again.
+			 */
+			result = isc_resource_getcurlimit(
+							isc_resource_openfiles,
+							&manager->open_max);
+			if (result != ISC_R_SUCCESS)
+				manager->open_max = 64;
+		} else
+			break;
+	}
+	swait_private.nevents = n;
 #elif defined(USE_SELECT)
 	memmove(manager->read_fds_copy, manager->read_fds, manager->fd_bufsize);
 	memmove(manager->write_fds_copy, manager->write_fds,