Messages in this thread | | | Date | Tue, 6 Oct 2009 21:47:48 -0700 | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 0/3] rcu: prevent hangs by simplifying rcu_barrier/CPU-hotplug, fix lockdep complaint |
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This patchset fixes a couple of issues with TREE_PREEMPT_RCU:
1. The current implementation of rcu_barrier() waits for any prior CPU-hotplug operation to complete. This code path has resulted in some hangs, so first move this code from rcupdate.c to rcutree.c and then use a simpler algorithm that avoids the waiting, eliminating the possibility of such hangs.
2. The lockdep facility complains from time to time due to the fact that certain combinations of CPU-hotplug operations can cause the TREE_PREEMPT_RCU code to acquire the root rcu_node structure's lock while holding a leaf rcu_node structure's lock. This patch places the root rcu_node structure's lock into its own lockdep class to prevent this false positive.
Ingo, please rewind tip/core/rcu to commit #135c8aea before applying this series, as these patches really need to go into 2.6.32. Reworked and retested rcutiny (for 2.6.33, as Linus requested) will follow in a few days. Or more patches for more bug fixes, as the case may be. ;-)
b/kernel/rcupdate.c | 120 ----------------------------------- b/kernel/rcutree.c | 120 +++++++++++++++++++++++++++++++++++ b/kernel/rcutree.h | 11 ++- b/kernel/rcutree_plugin.h | 34 ++++++++++ b/kernel/rcutree_trace.c | 5 - kernel/rcutree.c | 156 ++++++++++++++++++++++++---------------------- 6 files changed, 248 insertions(+), 198 deletions(-)
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