### Description
S-CSCF stops processing REGISTER and INVITE requests.
### Troubleshooting
Gdb stack traces revealed several processes trying to do lock_udmain()
unsuccessfully.
Adding more debug pointed to the direction of ims_registrar_scscf
[lookup.c:107]: lookup().
This function does lock_udomain() with one "slot" and releases it with another.
The lookup()
[locks](https://github.com/kamailio/kamailio/blob/48de203fda213749ac1e6fdb081c22dd701f85c4/src/modules/ims_registrar_scscf/lookup.c#L107)
domain with one value in the **aor** but before unlocking it at lockup.c:209
the said
aor is
[changed](https://github.com/kamailio/kamailio/blob/48de203fda213749ac1e6fdb081c22dd701f85c4/src/modules/ims_registrar_scscf/lookup.c#L134).
Aor points to the URI that is rewritten and therefore the wrong slot is
[unlocked](https://github.com/kamailio/kamailio/blob/48de203fda213749ac1e6fdb081c22dd701f85c4/src/modules/ims_registrar_scscf/lookup.c#L209).
In the log below the locked slot is 461 while unlocked is 427.
9(791) DEBUG: ims_registrar_scscf [lookup.c:90]: lookup(): looking for any type
of terminal
9(791) DEBUG: ims_registrar_scscf [lookup.c:103]: lookup(): Looking for
tel:+46xx
9(791) DEBUG: ims_usrloc_scscf [udomain.c:445]: lock_ulslot(): LOCKING UDOMAIN
SLOT [**461**]
9(791) DEBUG: ims_registrar_scscf [lookup.c:119]: lookup(): Found a valid
contact [sip:10.110.2.199:5060;alias=10.110.2.19950602]
9(791) DEBUG: [core/parser/parse_rr.c:464]: get_path_dst_uri(): path for
branch: 'sip:t...@pcscf.yyy.xxx.3gppnetwork.org;lr'
9(791) DEBUG: ims_usrloc_scscf [udomain.c:465]: unlock_ulslot(): UN-LOCKING
UDOMAIN SLOT [**427**]
Reproduction
Debugging Data
```
(gdb) bt #0 syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
#1 0x7fecd3f61dbd in futex_get (lock=0x7feccf6a2214) at
../../core/mem/../futexlock.h:108 #2 0x7fecd3f6832e in lock_ulslot
(_d=0x7feccf70a718, i=461) at udomain.c:450
#3 0x7fecd3f68273 in lock_udomain (_d=0x7feccf70a718, _aor=0x7feccf72e5a8)
at udomain.c:424 #4 0x7fecd3ccd375 in update_contacts (msg=0x7fecd3f1b6c0
<_pv_treq>, _d=0x7feccf70a718, public_identity=0x7feccf73e0c8,
assignment_type=2, s=0x7fff31beac58, ccf1=0x7fff31beac80, ccf2=0x7fff31beac90,
ecf1=0x7fff31beaca0, ecf2=0x7fff31beacb0, contact_header=0x7feccf73e0e0) at
save.c:886 #5 0x7fecd3c6cbe5 in async_cdp_callback (is_timeout=0,
param=0x7feccf73e0a0, saa=0x7feccf7b9430, elapsed_msecs=59) at cxdx_sar.c:252
#6 0x7fecd460fb18 in api_callback (p=0x7feccf69cd18, msg=0x7feccf7b9430,
ptr=0x0) at api_process.c:120 #7 0x7fecd46868aa in worker_process (id=0) at
worker.c:346
#8 0x7fecd464636b in diameter_peer_start (blocking=0) at
diameter_peer.c:242
#9 0x7fecd4622666 in cdp_child_init (rank=0) at cdp_mod.c:243 #10
0x005d2fbc in init_mod_child (m=0x7fecd940f8a0, rank=0) at
core/sr_module.c:943 #11 0x005d2c5e in init_mod_child
(m=0x7fecd9410550, rank=0) at core/sr_module.c:939 #12 0x005d2c5e in
init_mod_child (m=0x7fecd9410958, rank=0) at core/sr_module.c:939 #13
0x005d2c5e in init_mod_child (m=0x7fecd9410d68, rank=0) at
core/sr_module.c:939 #14 0x005d2c5e in init_mod_child
(m=0x7fecd9411560, rank=0) at core/sr_module.c:939 #15 0x005d2c5e in
init_mod_child (m=0x7fecd9411aa0, rank=0) at core/sr_module.c:939 #16
0x005d2c5e in init_mod_child (m=0x7fecd9411f00, rank=0) at
core/sr_module.c:939 #17 0x005d3390 in init_child (rank=0) at
core/sr_module.c:970 #18 0x0042539c in main_loop () at main.c:1701 #19
0x0042bdd5 in main (argc=6, argv=0x7fff31beb998) at main.c:2638
```
Log Messages
```
9(791) DEBUG: ims_registrar_scscf [lookup.c:90]: lookup(): looking for any type
of terminal
9(791) DEBUG: ims_registrar_scscf [lookup.c:103]: lookup(): Looking for
tel:+46xx
9(791) DEBUG: ims_usrloc_scscf [udomain.c:445]: lock_ulslot(): LOCKING UDOMAIN
SLOT [461]
9(791) DEBUG: ims_registrar_scscf [lookup.c:119]: lookup(): Found a valid
contact [sip:10.110.2.199:5060;alias=10.110.2.19950602]
9(791) DEBUG: [core/parser/parse_rr.c:464]: get_path_dst_uri(): path for
branch: 'sip:t...@pcscf.yyy.xxx.3gppnetwork.org;lr'
9(791) DEBUG: ims_usrloc_scscf [udomain.c:465]: unlock_ulslot(): UN-LOCKING
UDOMAIN SLOT [427]
```
SIP Traffic
```
(paste your sip traffic here)
```
### Possible Solutions
Make a copy of the aor string.
### Additional Information
* **Kamailio Version** - output of `kamailio -v`
```
version: kamailio 5.1.5 (x86_64/linux)
flags: STATS: Off, USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS,
DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MEM, SHM_MMAP, PKG_MALLOC, Q_MALLOC,
F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT,
USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES
ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE 262144 MAX_URI_SIZE 1024,
BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB
po
