linux-kernel - [ 034/187] dummy: fix rcu_sched self-detected stalls

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Message-Id: <20120712191525.468597068@linuxfoundation.org>
Date:	Thu, 12 Jul 2012 15:33:10 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 034/187] dummy: fix rcu_sched self-detected stalls

From: Greg KH <gregkh@...uxfoundation.org>

3.4-stable review patch.  If anyone has any objections, please let me know.

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


From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit 16b0dc29c1af9df341428f4c49ada4f626258082 ]

Trying to "modprobe dummy numdummies=30000" triggers :

INFO: rcu_sched self-detected stall on CPU { 8} (t=60000 jiffies)

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

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

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/dummy.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/net/dummy.c
+++ b/drivers/net/dummy.c
@@ -187,8 +187,10 @@ static int __init dummy_init_module(void
 	rtnl_lock();
 	err = __rtnl_link_register(&dummy_link_ops);
 
-	for (i = 0; i < numdummies && !err; i++)
+	for (i = 0; i < numdummies && !err; i++) {
 		err = dummy_init_one();
+		cond_resched();
+	}
 	if (err < 0)
 		__rtnl_link_unregister(&dummy_link_ops);
 	rtnl_unlock();


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