Commit-ID: 22a767269a767b3ee91e4aaea353ac6bec6a912d Gitweb: http://git.kernel.org/tip/22a767269a767b3ee91e4aaea353ac6bec6a912d Author: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx> AuthorDate: Wed, 19 Sep 2012 08:52:32 -0700 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Sun, 23 Sep 2012 07:42:52 -0700 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@xxxxxxxxxxxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> --- kernel/rcutiny.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c index 2e073a2..e4c6a59 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) */ } /* -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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