Fixed deadlock between stream and ICE

[sauwming]

It is reported that a deadlock can occur between stream and ICE:

SIPMediaControl!pj_mutex_lock_ex+156 [C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\os_core_win32.c @ 1124]	  C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\os_core_win32.c @ 1124
SIPMediaControl!on_rx_rtp+411 [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 2077]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 2077
SIPMediaControl!srtp_rtp_cb+6d [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\transport_srtp.c @ 1552]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\transport_srtp.c @ 1552
SIPMediaControl!ice_on_rx_data+f2 [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\transport_ice.c @ 2572]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\transport_ice.c @ 2572
SIPMediaControl!ice_rx_data+34 [C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_strans.c @ 2287]	  C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_strans.c @ 2287
SIPMediaControl!pj_ice_sess_on_rx_pkt+1dd [C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_session.c @ 3742]	  C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_session.c @ 3742
SIPMediaControl!stun_on_rx_data+b5 [C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_strans.c @ 2369]	  C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_strans.c @ 2369
SIPMediaControl!on_data_recvfrom+104 [C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\stun_sock.c @ 1009]	  C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\stun_sock.c @ 1009
SIPMediaControl!ioqueue_on_read_complete+fc [C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\activesock.c @ 520 + 23]	  C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\activesock.c @ 520 + 23
SIPMediaControl!ioqueue_dispatch_read_event+21e [C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\ioqueue_common_abs.c @ 629]	  C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\ioqueue_common_abs.c @ 629
SIPMediaControl!pj_ioqueue_poll+3ac [C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\ioqueue_select.c @ 1128]	  C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\ioqueue_select.c @ 1128
SIPMediaControl!pjsip_endpt_handle_events2+8e [C:\UCS\External\pjsip\pjproject-2.14\pjsip\src\pjsip\sip_endpoint.c @ 746]	  C:\UCS\External\pjsip\pjproject-2.14\pjsip\src\pjsip\sip_endpoint.c @ 746
SIPMediaControl!worker_thread+50 [C:\UCS\External\pjsip\pjproject-2.14\pjsip\src\pjsua-lib\pjsua_core.c @ 807 + 30]	  C:\UCS\External\pjsip\pjproject-2.14\pjsip\src\pjsua-lib\pjsua_core.c @ 807 + 30
SIPMediaControl!thread_main+4a [C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\os_core_win32.c @ 538 + 7]	  C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\os_core_win32.c @ 538 + 7

SIPMediaControl!pj_mutex_lock_ex+156 [C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\os_core_win32.c @ 1124]	  C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\os_core_win32.c @ 1124
SIPMediaControl!grp_lock_acquire+36 [C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\lock.c @ 300]	  C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\lock.c @ 300
SIPMediaControl!send_data+b2 [C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_strans.c @ 1837]	  C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_strans.c @ 1837
SIPMediaControl!pj_ice_strans_sendto2+35 [C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_strans.c @ 1988]	  C:\UCS\External\pjsip\pjproject-2.14\pjnath\src\pjnath\ice_strans.c @ 1988
SIPMediaControl!transport_send_rtcp2+7d [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\transport_ice.c @ 2512]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\transport_ice.c @ 2512
SIPMediaControl!transport_send_rtcp+32 [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\transport_srtp.c @ 1417]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\transport_srtp.c @ 1417
SIPMediaControl!send_rtcp+26c [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 1211 + 15]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 1211 + 15
SIPMediaControl!check_tx_rtcp+46 [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 1270]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 1270
SIPMediaControl!put_frame_imp+3a0 [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 1556]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 1556
SIPMediaControl!put_frame+16b [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 1725]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\stream.c @ 1725
SIPMediaControl!write_port+1dd [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\conference.c @ 1862 + 1c]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\conference.c @ 1862 + 1c
SIPMediaControl!get_frame+5f8 [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\conference.c @ 2230]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\conference.c @ 2230
SIPMediaControl!clock_callback+9d [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\master_port.c @ 195]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\master_port.c @ 195
SIPMediaControl!clock_thread+c5 [C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\clock_thread.c @ 395]	  C:\UCS\External\pjsip\pjproject-2.14\pjmedia\src\pjmedia\clock_thread.c @ 395
SIPMediaControl!thread_main+4a [C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\os_core_win32.c @ 538 + 7]	  C:\UCS\External\pjsip\pjproject-2.14\pjlib\src\pj\os_core_win32.c @ 538 + 7

The issue occurs because of the added locking when sending RTCP in #3528 .

[nanangizz]

Is this deadlock scenario still possible?

• send side thread:
  1. got lock(rtcp_mutex)
  2. want lock(ice_mutex)
• receive side thread:
  1. got lock(ice_mutex)
  2. want lock(rtcp_mutex)

[sauwming]

You're right. I have checked that on_rx_rtcp() does not acquire lock, but missed the part that on_rx_rtp() can call send_rtcp() as well.

I haven't found a proper solution though. Some ideas:

• Revert Prevent data race in stream when sending RTCP #3528 (and reopen Data races in pjmedia stream #1973). The data race seems to be a relatively minor issue, especially if compared to the potential deadlock.
• Move send_rtcp() from on_rx_rtp() to check_tx_rtcp(). I'm not sure if there can be potential consequences of this though.

[nanangizz]

* Revert [Prevent data race in stream when sending RTCP #3528](https://github.com/pjsip/pjproject/pull/3528) (and reopen [Data races in pjmedia stream #1973](https://github.com/pjsip/pjproject/issues/1973)). The data race seems to be a relatively minor issue, especially if compared to the potential deadlock.

Perhaps only consider this if there is no 'easy' solution.

* Move `send_rtcp()` from `on_rx_rtp()` to `check_tx_rtcp()`. I'm not sure if there can be potential consequences of this though.

Not sure if I understand this correctly, If you mean removing send_rtp() from on_rx_rtp(), then it sounds like a major change, it may not be good for receive-only stream.

Btw, how about using transport group lock for RTCP?