Re: [PATCH] Fix scheduling-while-atomic problem in console_cpu_notify()

Srivatsa S. Bhat
2012-10-16T05:32:12Z

On 10/16/2012 10:05 AM, Paul E. McKenney wrote:
> On Mon, Oct 15, 2012 at 05:31:28PM -0700, Paul E. McKenney wrote:
>> The console_cpu_notify( function runs with interrupts disabled in
>> the CPU_DEAD case. It therefore cannot block, for example, as will
>> happen when it calls console_lock(). Therefore, remove the CPU_DEAD
>> leg of the switch statement to avoid this problem.
>>
>> Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
>
> s/CPU_DEAD/CPU_DYING/
>
> Apparently it is a bad idea to compose and send a patch while in a
> C++ standards committee meeting where people are arguing about async
> futures... Fixed patch below.
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> printk: Fix scheduling-while-atomic problem in console_cpu_notify()
>
> The console_cpu_notify( function runs with interrupts disabled in
> the CPU_DYING case. It therefore cannot block, for example, as will
> happen when it calls console_lock(). Therefore, remove the CPU_DYING
> leg of the switch statement to avoid this problem.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>

Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Regards,
Srivatsa S. Bhat

> diff --git a/kernel/printk.c b/kernel/printk.c
> index 66a2ea3..2d607f4 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -1890,7 +1890,6 @@ static int __cpuinit console_cpu_notify(struct notifier_block *self,
> switch (action) {
> case CPU_ONLINE:
> case CPU_DEAD:
> - case CPU_DYING:
> case CPU_DOWN_FAILED:
> case CPU_UP_CANCELED:
> console_lock();
>