|author||Paul E. McKenney <email@example.com>||2011-11-22 20:43:02 -0800|
|committer||Paul E. McKenney <firstname.lastname@example.org>||2011-12-11 10:32:02 -0800|
rcu: Eliminate RCU_FAST_NO_HZ grace-period hang
With the new implementation of RCU_FAST_NO_HZ, it was possible to hang RCU grace periods as follows: o CPU 0 attempts to go idle, cycles several times through the rcu_prepare_for_idle() loop, then goes dyntick-idle when RCU needs nothing more from it, while still having at least on RCU callback pending. o CPU 1 goes idle with no callbacks. Both CPUs can then stay in dyntick-idle mode indefinitely, preventing the RCU grace period from ever completing, possibly hanging the system. This commit therefore prevents CPUs that have RCU callbacks from entering dyntick-idle mode. This approach also eliminates the need for the end-of-grace-period IPIs used previously. Signed-off-by: Paul E. McKenney <email@example.com> Signed-off-by: Paul E. McKenney <firstname.lastname@example.org>
Diffstat (limited to 'include/trace')
1 files changed, 0 insertions, 1 deletions
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index debe453c9623..8dd6fcb94946 100644
@@ -287,7 +287,6 @@ TRACE_EVENT(rcu_dyntick,
* "No callbacks": Nothing to do, no callbacks on this CPU.
* "In holdoff": Nothing to do, holding off after unsuccessful attempt.
- * "Dyntick with callbacks": Callbacks remain, but RCU doesn't need CPU.
* "Begin holdoff": Attempt failed, don't retry until next jiffy.
* "More callbacks": Still more callbacks, try again to clear them out.
* "Callbacks drained": All callbacks processed, off to dyntick idle!