From The Jargon File (version 4.4.7, 29 Dec 2003):
sleep
vi.
1. [techspeak] To relinquish a claim (of a process on a multitasking
system) for service; to indicate to the scheduler that a process may be
deactivated until some given event occurs or a specified time delay
elapses.
2. In jargon, used very similarly to v. block; also in sleep on, syn.:
with block on. Often used to indicate that the speaker has relinquished a
demand for resources until some (possibly unspecified) external event: “
They can't get the fix I've been asking for into the next release, so I'm
going to sleep on it until the release, then start hassling them again.”