Remove the memmove call on dns_rbtnode_t structure that contains atomics

Calling the plain memmove on the structure that contains atomic members
triggers following TSAN warning (even when we don't really use the
atomic members in the code):

    WARNING: ThreadSanitizer: data race
      Read of size 8 at 0x000000000001 by thread T1 (mutexes: write M1, write M2):
	#0 memmove <null>
	#1 memmove /usr/include/x86_64-linux-gnu/bits/string_fortified.h:40:10
	#2 deletefromlevel lib/dns/rbt.c:2675:3
	#3 dns_rbt_deletenode lib/dns/rbt.c:2143:2
	#4 delete_node lib/dns/rbtdb.c
	#5 decrement_reference lib/dns/rbtdb.c:2202:4
	#6 prune_tree lib/dns/rbtdb.c:2259:3
	#7 dispatch lib/isc/task.c:1152:7
	#8 run lib/isc/task.c:1344:2

      Previous atomic write of size 8 at 0x000000000001 by thread T2 (mutexes: read M3):
	#0 __tsan_atomic64_fetch_sub <null>
	#1 decrement_reference lib/dns/rbtdb.c:2103:7
	#2 detachnode lib/dns/rbtdb.c:5440:6
	#3 dns_db_detachnode lib/dns/db.c:588:2
	#4 qctx_clean lib/ns/query.c:5104:3
	#5 ns_query_done lib/ns/query.c:10868:2
	#6 query_sign_nodata lib/ns/query.c
	#7 query_nodata lib/ns/query.c:8438:11
	#8 query_gotanswer lib/ns/query.c
	#9 query_lookup lib/ns/query.c:5624:10
	#10 ns__query_start lib/ns/query.c:5500:10
	#11 query_setup lib/ns/query.c:5224:11
	#12 ns_query_start lib/ns/query.c:11357:8
	#13 ns__client_request lib/ns/client.c:2166:3
	#14 udp_recv_cb lib/isc/netmgr/udp.c:414:2
	#15 uv__udp_recvmsg /home/ondrej/Projects/tsan/libuv/src/unix/udp.c
	#16 uv__udp_io /home/ondrej/Projects/tsan/libuv/src/unix/udp.c:180:5
	#17 uv__io_poll /home/ondrej/Projects/tsan/libuv/src/unix/linux-core.c:461:11
	#18 uv_run /home/ondrej/Projects/tsan/libuv/src/unix/core.c:385:5
	#19 nm_thread lib/isc/netmgr/netmgr.c:500:11

      Location is heap block of size 132 at 0x000000000030 allocated by thread T3:
	#0 malloc <null>
	#1 default_memalloc lib/isc/mem.c:713:8
	#2 mem_get lib/isc/mem.c:622:8
	#3 mem_allocateunlocked lib/isc/mem.c:1268:8
	#4 isc___mem_allocate lib/isc/mem.c:1288:7
	#5 isc__mem_allocate lib/isc/mem.c:2453:10
	#6 isc___mem_get lib/isc/mem.c:1037:11
	#7 isc__mem_get lib/isc/mem.c:2432:10
	#8 create_node lib/dns/rbt.c:2239:9
	#9 dns_rbt_addnode lib/dns/rbt.c:1435:12
	#10 findnodeintree lib/dns/rbtdb.c:2895:12
	#11 findnode lib/dns/rbtdb.c:2941:10
	#12 dns_db_findnode lib/dns/db.c:439:11
	#13 diff_apply lib/dns/diff.c:306:5
	#14 dns_diff_apply lib/dns/diff.c:459:10
	#15 do_one_tuple lib/ns/update.c:444:11
	#16 update_one_rr lib/ns/update.c:495:10
	#17 update_action lib/ns/update.c:3123:6
	#18 dispatch lib/isc/task.c:1152:7
	#19 run lib/isc/task.c:1344:2

      Mutex M1 is already destroyed.

      Mutex M2 is already destroyed.

      Mutex M3 is already destroyed.

      Thread T1 (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

      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_nm_start lib/isc/netmgr/netmgr.c:223:3
	#3 create_managers bin/named/main.c:909:15
	#4 setup bin/named/main.c:1223:11
	#5 main bin/named/main.c:1523:2

      Thread T3 (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 memmove

diff --git a/lib/dns/rbt.c b/lib/dns/rbt.c
index cb9ba048ce79173ac02798c9f015027c633404b1..11ede9e12fdeca089460d134c4c6670c2c8bcc57 100644 (file)
--- a/lib/dns/rbt.c
+++ b/lib/dns/rbt.c
@@ -2636,7 +2636,8 @@ deletefromlevel(dns_rbtnode_t *item, dns_rbtnode_t **rootp) {
                 */
                child = LEFT(item);
        } else {
-               dns_rbtnode_t holder, *tmp = &holder;
+               dns_rbtnode_t *saved_parent, *saved_right;
+               int saved_color;
 
                /*
                 * This node has two children, so it cannot be directly
@@ -2672,7 +2673,9 @@ deletefromlevel(dns_rbtnode_t *item, dns_rbtnode_t **rootp) {
                 * information, which will be needed when linking up
                 * delete to the successor's old location.
                 */
-               memmove(tmp, successor, sizeof(dns_rbtnode_t));
+               saved_parent = PARENT(successor);
+               saved_right = RIGHT(successor);
+               saved_color = COLOR(successor);
 
                if (IS_ROOT(item)) {
                        *rootp = successor;
@@ -2698,28 +2701,27 @@ deletefromlevel(dns_rbtnode_t *item, dns_rbtnode_t **rootp) {
 
                /*
                 * Now relink the node to be deleted into the
-                * successor's previous tree location.  PARENT(tmp)
-                * is the successor's original parent.
+                * successor's previous tree location.
                 */
                INSIST(!IS_ROOT(item));
 
-               if (PARENT(tmp) == item) {
+               if (saved_parent == item) {
                        /*
                         * Node being deleted was successor's parent.
                         */
                        RIGHT(successor) = item;
                        PARENT(item) = successor;
                } else {
-                       LEFT(PARENT(tmp)) = item;
-                       PARENT(item) = PARENT(tmp);
+                       LEFT(saved_parent) = item;
+                       PARENT(item) = saved_parent;
                }
 
                /*
                 * Original location of successor node has no left.
                 */
                LEFT(item) = NULL;
-               RIGHT(item) = RIGHT(tmp);
-               COLOR(item) = COLOR(tmp);
+               RIGHT(item) = saved_right;
+               COLOR(item) = saved_color;
        }
 
        /*