From: Mark Andrews <marka@isc.org>
Date: Wed, 23 Sep 2020 03:54:06 +0000 (+1000)
Subject: It appears that you can't change what you are polling for while connecting.
X-Git-Tag: v9.17.6~36^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c37b251eb98d673716ad1e9d80e6f4deeb23bdb9;p=thirdparty%2Fbind9.git

It appears that you can't change what you are polling for while connecting.

    WARNING: ThreadSanitizer: data race
    Read of size 8 at 0x000000000001 by thread T1 (mutexes: write M1):
    #0 epoll_ctl <null>
    #1 watch_fd lib/isc/unix/socket.c:704:8
    #2 wakeup_socket lib/isc/unix/socket.c:897:11
    #3 process_ctlfd lib/isc/unix/socket.c:3362:3
    #4 process_fds lib/isc/unix/socket.c:3275:10
    #5 netthread lib/isc/unix/socket.c:3516:10

    Previous write of size 8 at 0x000000000001 by thread T2 (mutexes: write M2):
    #0 connect <null>
    #1 isc_socket_connect lib/isc/unix/socket.c:4737:7
    #2 resquery_send lib/dns/resolver.c:2892:13
    #3 fctx_query lib/dns/resolver.c:2202:12
    #4 fctx_try lib/dns/resolver.c:4300:11
    #5 resquery_connected lib/dns/resolver.c:3130:4
    #6 dispatch lib/isc/task.c:1152:7
    #7 run lib/isc/task.c:1344:2

    Location is file descriptor 513 created by thread T2 at:
    #0 connect <null>
    #1 isc_socket_connect lib/isc/unix/socket.c:4737:7
    #2 resquery_send lib/dns/resolver.c:2892:13
    #3 fctx_query lib/dns/resolver.c:2202:12
    #4 fctx_try lib/dns/resolver.c:4300:11
    #5 resquery_connected lib/dns/resolver.c:3130:4
    #6 dispatch lib/isc/task.c:1152:7
    #7 run lib/isc/task.c:1344:2

    Mutex M1 (0x000000000016) created at:
    #0 pthread_mutex_init <null>
    #1 isc__mutex_init lib/isc/pthreads/mutex.c:288:8
    #2 setup_thread lib/isc/unix/socket.c:3584:3
    #3 isc_socketmgr_create2 lib/isc/unix/socket.c:3825:3
    #4 create_managers bin/named/main.c:932:11
    #5 setup bin/named/main.c:1223:11
    #6 main bin/named/main.c:1523:2

    Mutex M2 is already destroyed.

    Thread T1 'isc-socket-1' (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:73:8
    #2 isc_socketmgr_create2 lib/isc/unix/socket.c:3826:3
    #3 create_managers bin/named/main.c:932:11
    #4 setup bin/named/main.c:1223:11
    #5 main bin/named/main.c:1523:2

    Thread T2 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:73:8
    #2 isc_taskmgr_create lib/isc/task.c:1434:3
    #3 create_managers bin/named/main.c:915:11
    #4 setup bin/named/main.c:1223:11
    #5 main bin/named/main.c:1523:2

    SUMMARY: ThreadSanitizer: data race in epoll_ctl
---

diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index 570f91870a3..e3e49689e8f 100644
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -701,7 +701,13 @@ watch_fd(isc__socketthread_t *thread, int fd, int msg) {
 	event.data.fd = fd;
 
 	op = (oldevents == 0U) ? EPOLL_CTL_ADD : EPOLL_CTL_MOD;
+	if (thread->fds[fd] != NULL) {
+		LOCK(&thread->fds[fd]->lock);
+	}
 	ret = epoll_ctl(thread->epoll_fd, op, fd, &event);
+	if (thread->fds[fd] != NULL) {
+		UNLOCK(&thread->fds[fd]->lock);
+	}
 	if (ret == -1) {
 		if (errno == EEXIST) {
 			UNEXPECTED_ERROR(__FILE__, __LINE__,