Hi Julia,
On 01/02/2019 17:36, Julia Cartwright wrote:
On Fri, Feb 01, 2019 at 03:30:58PM +0000, Julien Grall wrote:
Hi Julien,
On 07/01/2019 15:06, Julien Thierry wrote:
vgic_irq->irq_lock must always be taken with interrupts disabled as
it is used in interrupt context.
I am a bit confused with the reason here. The code mention that ap_list_lock
could be taken from the timer interrupt handler interrupt. I assume it
speaks about the handler kvm_arch_timer_handler. Looking at the
configuration of the interrupt, the flag IRQF_NO_THREAD is not set, so the
interrupt should be threaded when CONFIG_PREEMPT_FULL is set. If my
understanding is correct, this means the interrupt thread would sleep if it
takes the spinlock.
Did I miss anything? Do you have an exact path where the vGIC is actually
called from an interrupt context?
The part you're missing is that percpu interrupts are not force
threaded:
static int irq_setup_forced_threading(struct irqaction *new)
{
if (!force_irqthreads)
return 0;
if (new->flags & (IRQF_NO_THREAD | IRQF_PERCPU | IRQF_ONESHOT))
return 0;
/* ...*/
}
Thank you for the pointer! I think it would be worth mentioning in the commit
message that per-cpu interrupts are not threaded.
Best regards,
--
Julien Grall
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