Comment 105 for bug 1684993

Reviewed: https://review.opencontrail.org/46530
Committed: http://github.com/Juniper/contrail-third-party/commit/c0c55a572419876af53112ac0e4de5ba6d06de81
Submitter: Zuul v3 CI (<email address hidden>)
Branch: master

commit c0c55a572419876af53112ac0e4de5ba6d06de81
Author: Ananth Suryanarayana <email address hidden>
Date: Wed Sep 19 18:50:49 2018 -0700

Do not insert already sleeping tbb task back into sleeping list

During testing, it was found that tbb sleeping threads singly linked
list was corrupted and had become circular. This seemingly caused
my_slack count to get permanently stuck at -1, as the sleeping list
traversal would potentially never end.

During testing, using a specific assert, it was confirmed that duplicate
insertion did happen.

Fixed it by modifying the sleeing threads singly linked list into a
doubly linked list and then making sure that a thread if already in
the list is never prepended back as the head of the list.

https://github.com/01org/tbb/issues/86

Change-Id: I84993a23b4524f19c42e4166015c9216466c6865
Closes-Bug: #1684993