Re: [PATCH 2/6] irq_work: Implement remote queueing

["Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>]

On 06/25/2014 10:47 AM, Peter Zijlstra wrote:
> On Wed, Jun 25, 2014 at 07:12:34AM +0200, Peter Zijlstra wrote:
>> On Tue, Jun 24, 2014 at 02:33:41PM -0600, Stephen Warren wrote:
>>> On 06/10/2014 09:15 AM, Frederic Weisbecker wrote:
>>>> irq work currently only supports local callbacks. However its code
>>>> is mostly ready to run remote callbacks and we have some potential user.

[...]

>> Right you are.. I think I'll just remove the BUG_ON(), Frederic?
> 
> Something a little so like:
> 
> ---
> Subject: irq_work: Remove BUG_ON in irq_work_run_list()

I think this should be irq_work_run(), see below...

> From: Peter Zijlstra <peterz@infradead.org>
> Date: Wed Jun 25 07:13:07 CEST 2014
> 
> Because of a collision with 8d056c48e486 ("CPU hotplug, smp: flush any
> pending IPI callbacks before CPU offline"), which ends up calling
> hotplug_cfd()->flush_smp_call_function_queue()->run_irq_work(), which


s/run_irq_work/irq_work_run


> is not from IRQ context.
> 
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Reported-by: Stephen Warren <swarren@wwwdotorg.org>
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> ---
>  kernel/irq_work.c |    2 --
>  1 file changed, 2 deletions(-)
> 
> --- a/kernel/irq_work.c
> +++ b/kernel/irq_work.c
> @@ -130,8 +130,6 @@ static void irq_work_run_list(struct lli
>  	struct irq_work *work;
>  	struct llist_node *llnode;
>  
> -	BUG_ON(!irqs_disabled());
> -

I don't think irqs_disabled() is the problematic condition, since
hotplug_cfg() invokes irq_work_run() from CPU_DYING context (which has
irqs disabled). I guess you meant to remove the in_irq() check inside
irq_work_run() instead?

Regards,
Srivatsa S. Bhat

>  	if (llist_empty(list))
>  		return;
>  
>