linux-kernel - [PATCH] rcu: don't use __this_cpu

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Date:	Sun, 28 Dec 2014 11:49:40 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	linux-kernel@...r.kernel.org
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <laijs@...fujitsu.com>
Subject: [PATCH] rcu: don't use __this_cpu_* from preemptible context

Commit "rcu: Make cond_resched_rcu_qs() apply to normal RCU flavors" has added
debug code which tries to read from __this_cpu in a preemptible code, which
doesn't work too well.

Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
---
 kernel/rcu/tree_trace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c
index a9b79ca..fbb6240 100644
--- a/kernel/rcu/tree_trace.c
+++ b/kernel/rcu/tree_trace.c
@@ -122,7 +122,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
 		   cpu_is_offline(rdp->cpu) ? '!' : ' ',
 		   ulong2long(rdp->completed), ulong2long(rdp->gpnum),
 		   rdp->passed_quiesce,
-		   rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr),
+		   rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu),
 		   rdp->qs_pending);
 	seq_printf(m, " dt=%d/%llx/%d df=%lu",
 		   atomic_read(&rdp->dynticks->dynticks),
-- 
1.7.10.4

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