The realtime preemption endgame

Posted Aug 5, 2009 21:24 UTC (Wed) by PaulMcKenney (✭ supporter ✭, #9624)
In reply to: The realtime preemption endgame by tertium
Parent article: The realtime preemption endgame

OK, you lost me on this one. Why can't task B be preempted while spinning? What am I missing here?

The realtime preemption endgame

Posted Aug 5, 2009 21:43 UTC (Wed) by tertium (guest, #56169) [Link] (2 responses)

I was actually looking at the following phrase in the article: "Code holding spinlocks also cannot be preempted; doing so would cause serious latencies (at best) or deadlocks." Am I confused?

The realtime preemption endgame

Posted Aug 5, 2009 22:17 UTC (Wed) by tertium (guest, #56169) [Link] (1 responses)

Indeed, it seems I am: "code holding a spinlock" != "code spinning". My apologies.

By the way, in your scenario (if I'm not off the mark again) at the step 5, the task A wouldn't spin, since B isn't running. Instead, A would block immediately, awakening B and taking the lock.

The realtime preemption endgame

Posted Aug 5, 2009 22:47 UTC (Wed) by PaulMcKenney (✭ supporter ✭, #9624) [Link]

Exactly! :-)