linux-kernel - [15/84] ifb: fix rcu_sched self-detected stalls

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Message-ID: <lsq.1375276989.102556961@decadent.org.uk>
Date:	Wed, 31 Jul 2013 15:23:09 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"dingtianhong" <dingtianhong@...wei.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [15/84] ifb: fix rcu_sched self-detected stalls

3.2.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: dingtianhong <dingtianhong@...wei.com>

[ Upstream commit 440d57bc5ff55ec1efb3efc9cbe9420b4bbdfefa ]

According to the commit 16b0dc29c1af9df341428f4c49ada4f626258082
(dummy: fix rcu_sched self-detected stalls)

Eric Dumazet fix the problem in dummy, but the ifb will occur the
same problem like the dummy modules.

Trying to "modprobe ifb numifbs=30000" triggers :

INFO: rcu_sched self-detected stall on CPU

After this splat, RTNL is locked and reboot is needed.

We must call cond_resched() to avoid this, even holding RTNL.

Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/ifb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index 46b5f5f..4924a1e 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -291,8 +291,10 @@ static int __init ifb_init_module(void)
 	rtnl_lock();
 	err = __rtnl_link_register(&ifb_link_ops);
 
-	for (i = 0; i < numifbs && !err; i++)
+	for (i = 0; i < numifbs && !err; i++) {
 		err = ifb_init_one(i);
+		cond_resched();
+	}
 	if (err)
 		__rtnl_link_unregister(&ifb_link_ops);
 	rtnl_unlock();

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