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authorPaul E. McKenney <paul.mckenney@linaro.org>2011-11-22 20:43:02 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-12-11 10:32:02 -0800
commitf535a607c13c7b674e0788ca5765779aa74a01c3 (patch)
tree433a07d16ff11d9f67e7991831cebf3cadfd9939 /include/trace
parent84ad00cb61f1cb21f0b63bc6f7dc254399eb3830 (diff)
downloadlinux-linaro-stable-f535a607c13c7b674e0788ca5765779aa74a01c3.tar.gz
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 <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/trace')
-rw-r--r--include/trace/events/rcu.h1
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
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -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!