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Merge branch 'urgent-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/urgent

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Pull two RCU fixes from Paul E. McKenney:

" - Complete the work of commit dd56af42bd (rcu: Eliminate deadlock
    between CPU hotplug and expedited grace periods), which was
    intended to allow synchronize_sched_expedited() to be safely
    used when holding locks acquired by CPU-hotplug notifiers.
    This commit makes the put_online_cpus() avoid the deadlock
    instead of just handling the get_online_cpus().

  - Complete the work of commit 35ce7f29a4 (rcu: Create rcuo
    kthreads only for onlined CPUs), which was intended to allow
    RCU to avoid allocating unneeded kthreads on systems where the
    firmware says that there are more CPUs than are really present.
    This commit makes rcu_barrier() aware of the mismatch, so that
    it doesn't hang waiting for non-existent CPUs. "

Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
2014-10-30 07:37:37 +01:00
parent 5631b8fba6 d7e2993396
commit 21ee24bf5b
5 changed files with 66 additions and 15 deletions
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18
include/trace/events/rcu.h
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@@ -660,18 +660,18 @@ TRACE_EVENT(rcu_torture_read,
/*
* Tracepoint for _rcu_barrier() execution. The string "s" describes
* the _rcu_barrier phase:
* "Begin": rcu_barrier_callback() started.
* "Check": rcu_barrier_callback() checking for piggybacking.
* "EarlyExit": rcu_barrier_callback() piggybacked, thus early exit.
* "Inc1": rcu_barrier_callback() piggyback check counter incremented.
* "Offline": rcu_barrier_callback() found offline CPU
* "OnlineNoCB": rcu_barrier_callback() found online no-CBs CPU.
* "OnlineQ": rcu_barrier_callback() found online CPU with callbacks.
* "OnlineNQ": rcu_barrier_callback() found online CPU, no callbacks.
* "Begin": _rcu_barrier() started.
* "Check": _rcu_barrier() checking for piggybacking.
* "EarlyExit": _rcu_barrier() piggybacked, thus early exit.
* "Inc1": _rcu_barrier() piggyback check counter incremented.
* "OfflineNoCB": _rcu_barrier() found callback on never-online CPU
* "OnlineNoCB": _rcu_barrier() found online no-CBs CPU.
* "OnlineQ": _rcu_barrier() found online CPU with callbacks.
* "OnlineNQ": _rcu_barrier() found online CPU, no callbacks.
* "IRQ": An rcu_barrier_callback() callback posted on remote CPU.
* "CB": An rcu_barrier_callback() invoked a callback, not the last.
* "LastCB": An rcu_barrier_callback() invoked the last callback.
* "Inc2": rcu_barrier_callback() piggyback check counter incremented.
* "Inc2": _rcu_barrier() piggyback check counter incremented.
* The "cpu" argument is the CPU or -1 if meaningless, the "cnt" argument
* is the count of remaining callbacks, and "done" is the piggybacking count.
*/