glusterd hung while volume set operations were running in a loop. This is  the backtrace when the process was attached to gdb

#0  0x0000003c8460caab in pthread_once () from /lib64/libpthread.so.0
#1  0x0000003c83efb7e4 in backtrace () from /lib64/libc.so.6
#2  0x0000003c83e6f83b in __libc_message () from /lib64/libc.so.6
#3  0x0000003c83e75146 in malloc_printerr () from /lib64/libc.so.6
#4  0x0000003c83e75571 in malloc_consolidate () from /lib64/libc.so.6
#5  0x0000003c83e780e2 in _int_malloc () from /lib64/libc.so.6
#6  0x0000003c83e791a8 in calloc () from /lib64/libc.so.6
#7  0x0000003c83a0acaf in _dl_new_object () from /lib64/ld-linux-x86-64.so.2
#8  0x0000003c83a0717e in _dl_map_object_from_fd () from /lib64/ld-linux-x86-64.so.2
#9  0x0000003c83a0831a in _dl_map_object () from /lib64/ld-linux-x86-64.so.2
#10 0x0000003c83a128d2 in dl_open_worker () from /lib64/ld-linux-x86-64.so.2
#11 0x0000003c83a0e0a6 in _dl_catch_error () from /lib64/ld-linux-x86-64.so.2
#12 0x0000003c83a1238a in _dl_open () from /lib64/ld-linux-x86-64.so.2
#13 0x0000003c83f22f20 in do_dlopen () from /lib64/libc.so.6
#14 0x0000003c83a0e0a6 in _dl_catch_error () from /lib64/ld-linux-x86-64.so.2
#15 0x0000003c83f23077 in __libc_dlopen_mode () from /lib64/libc.so.6
#16 0x0000003c83efb6e5 in init () from /lib64/libc.so.6
#17 0x0000003c8460cab3 in pthread_once () from /lib64/libpthread.so.0
#18 0x0000003c83efb7e4 in backtrace () from /lib64/libc.so.6
#19 0x0000003c83e6f83b in __libc_message () from /lib64/libc.so.6
#20 0x0000003c83e75146 in malloc_printerr () from /lib64/libc.so.6
#21 0x0000003c83e658cd in fclose@@GLIBC_2.2.5 () from /lib64/libc.so.6
#22 0x00007fd33602e494 in volgen_write_volfile (graph=0x7fff2737ee20,
    filename=0x7fff2737de20 "/etc/glusterd/vols/mirror/mirror.10.1.11.125.export-mirror.vol") at glusterd-volgen.c:1095
#23 0x00007fd33602e5cd in glusterd_generate_brick_volfile (volinfo=0x1b9d150, brickinfo=<value optimized out>) at glusterd-volgen.c:2283
#24 0x00007fd33602e7e1 in generate_brick_volfiles (volinfo=0x1b9d150) at glusterd-volgen.c:2344
#25 0x00007fd33602f596 in glusterd_create_volfiles_and_notify_services (volinfo=0x1b9d150) at glusterd-volgen.c:2453
#26 0x00007fd336009408 in glusterd_op_set_volume (dict=<value optimized out>) at glusterd-op-sm.c:5538
#27 0x00007fd3360102a8 in glusterd_op_commit_perform (op=<value optimized out>, dict=0x1ba15a0, op_errstr=0x7fff27380170,
    rsp_dict=<value optimized out>) at glusterd-op-sm.c:7449
#28 0x00007fd3360116a3 in glusterd_op_ac_send_commit_op (event=<value optimized out>, ctx=<value optimized out>) at glusterd-op-sm.c:6627
#29 0x00007fd3360052ae in glusterd_op_sm () at glusterd-op-sm.c:8285
#30 0x00007fd33602294c in glusterd3_1_stage_op_cbk (req=<value optimized out>, iov=<value optimized out>, count=<value optimized out>,
    myframe=0x7fd336cf9314) at glusterd-rpc-ops.c:1091
#31 0x00007fd337c7b365 in rpc_clnt_handle_reply (clnt=0x1370cc0, pollin=0x1371950) at rpc-clnt.c:741
#32 0x00007fd337c7b5b9 in rpc_clnt_notify (trans=<value optimized out>, mydata=0x1370cf0, event=<value optimized out>,
    data=<value optimized out>) at rpc-clnt.c:854
#33 0x00007fd337c76458 in rpc_transport_notify (this=<value optimized out>, event=<value optimized out>, data=<value optimized out>)
    at rpc-transport.c:919
#34 0x00007fd335d1a254 in socket_event_poll_in (this=0x16299c0) at socket.c:1647
#35 0x00007fd335d1a337 in socket_event_handler (fd=<value optimized out>, idx=3, data=0x16299c0, poll_in=1, poll_out=0,
    poll_err=<value optimized out>) at socket.c:1762
#36 0x00007fd337ec2504 in event_dispatch_epoll_handler (event_pool=0x1362360) at event.c:794
#37 event_dispatch_epoll (event_pool=0x1362360) at event.c:856
#38 0x0000000000405e99 in main (argc=1, argv=0x7fff27380d78) at glusterfsd.c:1509
f 22
#22 0x00007fd33602e494 in volgen_write_volfile (graph=0x7fff2737ee20, 
    filename=0x7fff2737de20 "/etc/glusterd/vols/mirror/mirror.10.1.11.125.export-mirror.vol") at glusterd-volgen.c:1095
1095                    fclose (f);
(gdb) p f
$3 = (FILE *) 0x1ba0ee0
(gdb) p *
A syntax error in expression, near `'.
(gdb) p *f
$4 = {_flags = 0, _IO_read_ptr = 0x1ba5130 "", _IO_read_end = 0x0, _IO_read_base = 0x0, _IO_write_base = 0x0, _IO_write_ptr = 0x0, 
  _IO_write_end = 0x0, _IO_buf_base = 0x0, _IO_buf_end = 0x0, _IO_save_base = 0x0, _IO_backup_base = 0x0, _IO_save_end = 0x0, 
  _markers = 0x0, _chain = 0x136d9a0, _fileno = -1, _flags2 = 0, _old_offset = 48, _cur_column = 0, _vtable_offset = -70 '\272', 
  _shortbuf = "\001", _lock = 0x1ba0fc0, _offset = -1, __pad1 = 0x0, __pad2 = 0x1ba0fd0, __pad3 = 0x0, __pad4 = 0x1ba1060, __pad5 = 0, 
  _mode = -1, _unused2 = '\000' <repeats 19 times>}
(gdb) l
1090     error:
1091
1092            if (ftmp)
1093                    GF_FREE (ftmp);
1094            if (f)
1095                    fclose (f);
1096
1097            gf_log ("", GF_LOG_ERROR, "failed to create volfile %s", filename);
1098
1099            return -1;
(gdb) l -
1080                    goto error;
1081            f = NULL;
1082
1083            if (rename (ftmp, filename) == -1)
1084                    goto error;
1085
1086            GF_FREE (ftmp);
1087
1088            return 0;
1089
(gdb)