linux-kernel - [ 054/143] ifb: fix rcu_sched self-detected stalls

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Date:	Mon, 12 May 2014 02:32:54 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Ding Tianhong <dingtianhong@...wei.com>,
	"David S. Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu>
Subject: [ 054/143] ifb: fix rcu_sched self-detected stalls

2.6.32-longterm 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>
[wt: 2.6.32: cond_resched() needs linux/sched.h]
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/net/ifb.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index 030913f..cfd5510 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -33,6 +33,7 @@
 #include <linux/etherdevice.h>
 #include <linux/init.h>
 #include <linux/moduleparam.h>
+#include <linux/sched.h>
 #include <net/pkt_sched.h>
 #include <net/net_namespace.h>
 
@@ -269,8 +270,10 @@ 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();
-- 
1.7.12.2.21.g234cd45.dirty



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