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Date: Fri, 25 Apr 2014 13:44:10 -0700
From: Randy Dunlap <rdunlap@infradead.org>
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To: Rik van Riel <riel@redhat.com>
CC: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        Richard Weinberger <richard@nod.at>, linux-next@vger.kernel.org,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        umgwanakikbuti@gmail.com
Subject: Re: mmotm 2014-04-24-13-07 uploaded
References: <20140424200837.727695A407C@corp2gmr1-2.hot.corp.google.com>	<535992DD.3060808@infradead.org> <20140425100459.7824f676@annuminas.surriel.com>
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On 04/25/14 07:04, Rik van Riel wrote:
> On Thu, 24 Apr 2014 15:40:29 -0700
> Randy Dunlap <rdunlap@infradead.org> wrote:
> 
> 
>> uml on x86_64 defconfig:
>>
>> drivers/built-in.o: In function `__handle_sysrq':
>> drivers/tty/sysrq.c:514: undefined reference to `rcu_sysrq_start'
>> drivers/tty/sysrq.c:558: undefined reference to `rcu_sysrq_end'
> 
> Randy, does the patch below fix it?

Hm, no, it does not.  I'll look into it.

> Mike, this patch should also address your concerns.
> 
> Andrew, this can be a -fix patch for the sysctl-rcu patch,
> assuming it fixes things :)
> 
> Signed-off-by: Rik van Riel <riel@redhat.com
> ---
>  drivers/tty/sysrq.c | 1 +
>  kernel/rcu/update.c | 3 ++-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index dd53af9..0867433 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -46,6 +46,7 @@
>  #include <linux/jiffies.h>
>  #include <linux/syscalls.h>
>  #include <linux/of.h>
> +#include <linux/rcupdate.h>
>  
>  #include <asm/ptrace.h>
>  #include <asm/irq_regs.h>
> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index 2ac3289..d22309c 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -322,7 +322,8 @@ int rcu_jiffies_till_stall_check(void)
>  
>  void rcu_sysrq_start(void)
>  {
> -	rcu_cpu_stall_suppress = 2;
> +	if (!rcu_cpu_stall_suppress)
> +		rcu_cpu_stall_suppress = 2;
>  }
>  
>  void rcu_sysrq_end(void)
> 


-- 
~Randy