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authorLi Zhong <zhong@linux.vnet.ibm.com>2012-09-19 08:52:32 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-09-23 07:42:52 -0700
commit22a767269a767b3ee91e4aaea353ac6bec6a912d (patch)
tree21ed83a572e345a81a9ed17182e0cf393712b003
parent58fac09566bb48592a09ef0fe0c7dbefa0cd2109 (diff)
rcu: Move TINY_RCU quiescent state out of extended quiescent state
TINY_RCU's rcu_idle_enter_common() invokes rcu_sched_qs() in order to inform the RCU core of the quiescent state implied by idle entry. Of course, idle is also an extended quiescent state, so that the call to rcu_sched_qs() speeds up RCU's invoking of any callbacks that might be queued. This speed-up is important when entering into dyntick-idle mode -- if there are no further scheduling-clock interrupts, the callbacks might never be invoked, which could result in a system hang. However, processing callbacks does event tracing, which in turn implies RCU read-side critical sections, which are illegal in extended quiescent states. This patch therefore moves the call to rcu_sched_qs() so that it precedes the point at which we inform lockdep that RCU has entered an extended quiescent state. Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
-rw-r--r--kernel/rcutiny.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 2e073a24d250..e4c6a598d6f7 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -75,9 +75,9 @@ static void rcu_idle_enter_common(long long newval)
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
+ rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
barrier();
rcu_dynticks_nesting = newval;
- rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
}
/*