Re: [ 08/68] dummy: fix rcu_sched self-detected stalls

From: Herton Ronaldo Krzesinski
Date: Fri Jul 13 2012 - 10:09:24 EST


On Thu, Jul 12, 2012 at 04:01:42PM -0700, Greg Kroah-Hartman wrote:
> From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
>
> 3.0-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
>
> From: Eric Dumazet <edumazet@xxxxxxxxxx>
>
> [ 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@xxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/net/dummy.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> --- a/drivers/net/dummy.c
> +++ b/drivers/net/dummy.c
> @@ -186,8 +186,10 @@ 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();

This cherry-pick for 3.0 has the same problem as the one that was
proposed to 3.2, build fails on i386/arm:

linux-stable/drivers/net/dummy.c: In function 'dummy_init_module':
linux-stable/drivers/net/dummy.c:191:3: error: implicit declaration of function 'cond_resched' [-Werror=implicit-function-declaration]

This will need an include for linux/sched.h as in 3.2 (the same proposed
patch for 3.4 shouldn't be affected).

> + }
> if (err < 0)
> __rtnl_link_unregister(&dummy_link_ops);
> rtnl_unlock();
>
>
> --
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Herton
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