Bug ID 465607: TMM cores with TMM log error 'Assertion "flow in use" failed.' when isuing FastHTTP.

Last Modified: Oct 06, 2020

Bug Tracker

Affected Product:  See more info
BIG-IP LTM(all modules)

Known Affected Versions:
11.3.0, 11.4.0, 11.4.1, 11.5.0, 11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.5.1 HF5, 11.5.1 HF6, 11.5.1 HF7, 11.5.1 HF8, 11.5.1 HF9, 11.5.10, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5

Fixed In:
12.0.0, 11.6.0 HF6, 11.5.2, 11.4.1 HF9

Opened: Jun 04, 2014
Severity: 3-Major
Related AskF5 Article:


TMM cores with the TMM log showing the error 'Assertion "flow in use" failed.' This is an infrequent race condition.


Traffic disrupted while tmm restarts.


This is an infrequent race condition. The actual set of events that leads to this core is unknown. However, this requires FastHTTP to be configured, and it is known that this happens when the FastHTTP connection is closing.


Do not use FastHTTP.

Fix Information

The system now provides checks to mitigate the race condition on close of FastHTTP to avoid the core.

Behavior Change