'central' failure on nrf52_pca10040

[alexandru-porosanu-nxp]

Describe the bug
When running the central sample on the latest master (33929cb), after a couple of connect/disconnects, an assertion is triggered, as per the log below

*** Booting Zephyr OS build zephyr-v2.1.0-1124-g33929cb96052  ***
Bluetooth initialized
Scanning successfully started
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
Disconnected: 5d:c0:95:93:b9:24 (random) (reason 0x16)
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
Disconnected: 5d:c0:95:93:b9:24 (random) (reason 0x16)
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
Disconnected: 5d:c0:95:93:b9:24 (random) (reason 0x16)
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
Disconnected: 5d:c0:95:93:b9:24 (random) (reason 0x16)
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
ASSERTION FAIL [e] @ ZEPHYR_BASE/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_conn.c:589

To Reproduce
Steps to reproduce the behavior:

1. cmake -Bbuild_nrf -G"Eclipse CDT4 - Ninja" -DBOARD=nrf52_pca10040 /work/b06830/zephyr/zephyr-source/samples/bluetooth/central
2. west flash -d build_nrf
3. the following assertion failed can be seen on the board's serial port:
   "ASSERTION FAIL [e] @ ZEPHYR_BASE/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_conn.c:589"

Expected behavior
The central sample should run endlessly with multiple connect/disconnect events

Impact
High

Screenshots or console output

*** Booting Zephyr OS build zephyr-v2.1.0-1124-g33929cb96052  ***
Bluetooth initialized
Scanning successfully started
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
Disconnected: 5d:c0:95:93:b9:24 (random) (reason 0x16)
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
Disconnected: 5d:c0:95:93:b9:24 (random) (reason 0x16)
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
Disconnected: 5d:c0:95:93:b9:24 (random) (reason 0x16)
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
Disconnected: 5d:c0:95:93:b9:24 (random) (reason 0x16)
Device found: 5d:c0:95:93:b9:24 (random) (RSSI -26)
Connected: 5d:c0:95:93:b9:24 (random)
ASSERTION FAIL [e] @ ZEPHYR_BASE/subsys/bluetooth/controller/ll_sw/nordic/lll/lll_conn.c:589

Environment (please complete the following information):

• Linux
• Zephyr SDK
• 33929cb

Additional context
Bisecting the tree shows that the first bad commit is the following:

commit 7417e6e
Author: Vinayak Kariappa Chettimada [email protected]
Date: Thu Dec 5 14:24:43 2019 +0530
Bluetooth: controller: split: conn handle invalidation on release

Move invalidation of connection handle to connection context
release done on release of terminate rx node.

Signed-off-by: Vinayak Kariappa Chettimada [email protected]

The PR introducing the commit is #20186

Reverting the aforementioned commit will enable the proper functionality for the central