There was a bug in the openib btl handling this valid sequence of
calls:
desc = btl_alloc ();
btl_free (desc);
When triggered the bug would cause either fragment loss or undefined
behavior (SEGV, etc). The problem occured because btl_alloc contained
the logic to modify the pending fragment (length, etc) and these
changes were not corrected if the fragment was freed instead of sent.
To fix this issue I 1) moved some of the coalescing logic to the
btl_send function, and 2) retry the coalesced fragment on btl_free
if it was never sent. This appears to completely address the issue.
9bae131589