[PROTON-2328] epoll proactor bug in tracking previous task used by a thread

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: proton-c-0.33.0
• Fix Version/s: proton-c-0.34.0
• Component/s: proton-c
• Environment: linux
• Assignee: Clifford Jansen
• Reporter: Clifford Jansen
• Created: 25/Jan/21 16:38
• Updated: 12/Apr/21 08:35
• Resolved: 25/Jan/21 17:11

Description

If an unassigned (ready) task and a free thread were each most recently working together, the epoll proactor tries to reassign them together for the next processing of the task, so that a warm memory cache may help performance.

One half of this pairing information is in tslot_t->prev_task. This value is always set to NULL, defeating the warm cache strategy. In unassign_thread() prev_task should be set from the local variable that contains the correct value and not the member variable tslot_t->task which is zeroed on an earlier line.