[LU-13005] Remove LNet event queuing subsystem (lib-eq)

Related — Sat, 3 Jul 2021 00:33:35 +0000

lib-eq provides a "event queue' which allows one thread to add events to a queue, and another to remove them, or wait for more.

Such a queue would be useful if LNet were accessed from user-space: allowing user-space to pluck events of a queue with minimal interaction with the kernel would be valuable. But lnet/eq is never used like that.

Almost all users for LNet/eq allocate a queue with zero slots and provide a call-back to be called for each event. This is a sensible approach when producer and consumer are in the same address space (i.e. both in the kernel).

The one exception is lnet_ping() which allocated a 2-element queue. lnet_ping() can easily be re-written to use a call-back, with a reduction in code size.

So let's remove the whole EQ subsystem and just use callbacks everywhere.

Whamcloud Community JIRA

[LU-13005] Remove LNet event queuing subsystem (lib-eq)