I am running a script which fires a VPP CLI in loop and keeps collecting some data. The CLI hangs after sometimes and the main thread gets locked at "mheap_maybe_lock". 
 
This is happening with other CLI commands as well and for me it is easily reproducible.
 
Here in a snip from "info thr"
{{ 2 Thread 0x7fb2337fc700 (LWP 5026) "vpp_stats" 0x00007fb4597bdf3d in nanosleep () at ../sysdeps/unix/syscall-template.S:81}}
* 1 Thread 0x7fb45be9c740 (LWP 5016) "vpp_main" 0x00007fb459f09a3b in mheap_maybe_lock (v=0x7fb398fc9000)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/mheap.c:66}}
 
 
 
Also, here is the Backtrace taken using GDB :
(gdb) bt
#0 0x00007fb459f09a3b in mheap_maybe_lock (v=0x7fb398fc9000)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/mheap.c:66}}
#1 mheap_get_aligned (v=0x7fb398fc9000, n_user_data_bytes=8, n_user_data_bytes@entry=5, align=<optimized out>, align@entry=4,
{{ align_offset=0, align_offset@entry=4, offset_return=offset_return@entry=0x7fb399c16698)}}
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/mheap.c:675}}
#2 0x00007fb459f33730 in clib_mem_alloc_aligned_at_offset (os_out_of_memory_on_failure=1, align_offset=4, align=4, size=5)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/mem.h:91}}
#3 vec_resize_allocate_memory (v=<optimized out>, length_increment=length_increment@entry=1, data_bytes=5,
{{ header_bytes=<optimized out>, header_bytes@entry=0, data_align=data_align@entry=4)}}
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/vec.c:59}}
#4 0x00007fb45b83477b in _vec_resize (data_align=<optimized out>, header_bytes=<optimized out>, data_bytes=<optimized out>,
{{ length_increment=<optimized out>, v=<optimized out>)}}
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/vec.h:142}}
#5 unix_cli_add_pending_output (uf=0x7fb399ccbd4c, buffer=0x7fb45b84a8d6 "\r", buffer_bytes=1, cf=<optimized out>)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vlib/unix/cli.c:528}}
#6 0x00007fb45b8374c0 in unix_cli_file_welcome (cf=0x7fb39a5d4a40, cm=<optimized out>)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vlib/unix/cli.c:1137}}
#7 0x00007fb459f3e1ab in timer_interrupt (signum=<optimized out>)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/timer.c:125}}
#8 <signal handler called>
#9 mheap_maybe_unlock (v=0x7fb398fc9000) at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/mheap.c:85
#10 mheap_get_aligned (v=0x7fb398fc9000, n_user_data_bytes=<optimized out>, n_user_data_bytes@entry=12, align=<optimized out>,
{{ align@entry=4, align_offset=0, align_offset@entry=4, offset_return=offset_return@entry=0x7fb399c16ef8)}}
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/mheap.c:717}}
#11 0x00007fb459f33730 in clib_mem_alloc_aligned_at_offset (os_out_of_memory_on_failure=1, align_offset=4, align=4, size=12)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/mem.h:91}}
#12 vec_resize_allocate_memory (v=v@entry=0x0, length_increment=1, data_bytes=12, header_bytes=<optimized out>,
{{ header_bytes@entry=0, data_align=data_align@entry=4)}}
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/vec.c:59}}
#13 0x00007fb45b83af23 in _vec_resize (data_align=0, header_bytes=0, data_bytes=<optimized out>,
{{ length_increment=<optimized out>, v=<optimized out>)}}
--Type <return> to continue, or q <return> to quit--
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/vec.h:142}}
#14 vlib_process_get_events (data_vector=<synthetic pointer>, vm=0x7fb45ba572c0 <vlib_global_main>)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vlib/node_funcs.h:562}}
#15 unix_cli_process (vm=0x7fb45ba572c0 <vlib_global_main>, rt=0x7fb399c06000, f=<optimized out>)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vlib/unix/cli.c:2414}}
#16 0x00007fb45b8037a6 in vlib_process_bootstrap (_a=<optimized out>)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vlib/main.c:1231}}
#17 0x00007fb459efe808 in clib_calljmp ()
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vppinfra/longjmp.S:110}}
#18 0x00007fb39a5c8c20 in ?? ()
#19 0x00007fb45b804ae9 in vlib_process_startup (f=0x0, p=0x7fb399c06000, vm=0x7fb45ba572c0 <vlib_global_main>)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vlib/main.c:1253}}
#20 dispatch_process (vm=0x7fb45ba572c0 <vlib_global_main>, p=0x7fb399c06000, last_time_stamp=0, f=0x0)
{{ at /root/vpp_dt/build-root/rpmbuild/vpp-18.01.1.0/build-data/../src/vlib/main.c:1296}}