On 06/25/2014 03:09 PM, Peter Zijlstra wrote:
> On Wed, Jun 25, 2014 at 11:36:57AM +0200, Peter Zijlstra wrote:
>> On Wed, Jun 25, 2014 at 12:07:05PM +0530, Srivatsa S. Bhat wrote:
>>> 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?
>>
>> Yes, clearly I should not get up at 6am.. :-) Let me go do a new one.
>
> ---
> Subject: irq_work: Remove BUG_ON in irq_work_run()
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> 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()->irq_work_run(), which
> is not from IRQ context.
>
> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Reported-by: Stephen Warren <swarren@xxxxxxxxxxxxx>
> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Link: http://lkml.kernel.org/n/tip-busatzs2gvz4v62258agipuf@xxxxxxxxxxxxxx
> ---
> kernel/irq_work.c | 12 +-----------
> 1 file changed, 1 insertion(+), 11 deletions(-)
>
> Index: linux-2.6/kernel/irq_work.c
> ===================================================================
> --- linux-2.6.orig/kernel/irq_work.c
> +++ linux-2.6/kernel/irq_work.c
> @@ -160,21 +160,11 @@ static void irq_work_run_list(struct lli
> }
> }
>
> -static void __irq_work_run(void)
Hmm, irq_work_cpu_notify() calls __irq_work_run() in the CPU_DYING
phase, to by-pass BUG_ON(!in_irq()). How about doing the same thing
from hotplug_cfd() as well?
> +static void irq_work_run(void)
> {
> irq_work_run_list(&__get_cpu_var(raised_list));
> irq_work_run_list(&__get_cpu_var(lazy_list));
> }
> -
> -/*
> - * Run the irq_work entries on this cpu. Requires to be ran from hardirq
> - * context with local IRQs disabled.
> - */
> -void irq_work_run(void)
> -{
> - BUG_ON(!in_irq());
> - __irq_work_run();
> -}
> EXPORT_SYMBOL_GPL(irq_work_run);
>
> /*
>
Regards,
Srivatsa S. Bhat
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