Re: ARM/gic-v4: deadlock occurred

[Guoheyi]

On 2019/7/15 19:13, Marc Zyngier wrote:
> On 15/07/2019 11:43, Guoheyi wrote:
> > On 2019/7/15 17:07, Marc Zyngier wrote:
> > > On 15/07/2019 07:32, Guoheyi wrote:
> > > > Hi Marc,
> > > >
> > > > The issue only occurs after applying the vlpi_map_rework patches, and we
> > > > can see the patches only affect VM; it changes its_create_device() a
> > > > little so it may affect host booting in some ways, so I took the lazy
> > > > way to send it out for some insights.
> > > >
> > > > I am suspecting below code; if alloc_lpis == false, what will happen?
> > > If !alloc_lpis, then we don't allocate the lpi_map, which is the
> > > intended effect.
> > >
> > > > Anyway, I will investigate more on this.
> > > >
> > > >
> > > > 	if  (alloc_lpis)  {
> > > > 		lpi_map  =  its_lpi_alloc(nvecs,  &lpi_base,  &nr_lpis);
> > > > 		if  (lpi_map)
> > > > 			col_map  =  kcalloc(nr_lpis,  sizeof(*col_map),
> > > > 					GFP_KERNEL);
> > > > 	}  else  {
> > > > 		col_map  =  kcalloc(nr_ites,  sizeof(*col_map),  GFP_KERNEL);
> > > > 		nr_lpis  =  0;
> > > > 		lpi_base  =  0;
> > > > 	}
> > > > 	if  (its->is_v4)
> > > > 		vlpi_map  =  kcalloc(nr_lpis,  sizeof(*vlpi_map),  GFP_KERNEL);
> > > >
> > > > 	if  (!dev  ||  !itt  ||   !col_map  ||  (!lpi_map  &&  alloc_lpis)  ||
> > > > 	(!vlpi_map  &&  its->is_v4))  {
> > > > 		kfree(dev);
> > > > 		kfree(itt);
> > > > 		kfree(lpi_map);
> > > > 		kfree(col_map);
> > > > 		kfree(vlpi_map);
> > > > 		return  NULL;
> > > > 	}
> > > How does this relate to the patch posted in this discussion? The
> > > proposed changes turn the locking from a mutex into a raw_spinlock.
> > I'm testing the patchset in
> > https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/vlpi-map-rework,
> > not only the patch posted in the mail directly. The first patch
> > *"**irqchip/gic-v3-its: Make vlpi_map allocations atomic" works well in
> > our internal tree, and my new testing is against the other 3 patches in
> > your vlpi-map-rework branch, as I promised. I'm sorry if I didn't state
> > this clearly.
> Ah, I had completely forgot about this branch. As I said, it is
> completely untested. I'll see if I can get some brain bandwidth in the
> next couple of weeks to get back to it...
Yes, a bit too long ago...

And finally I found the panic is caused by this patch: 
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=irq/vlpi-map-rework&id=fe3dd7e06ee0e82bade4f2a107ef6422e5c9021e

diff --git a/drivers/irqchip/irq-gic-v3-its.c 
b/drivers/irqchip/irq-gic-v3-its.c
index 18aa04b..6f55886 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -2458,6 +2458,8 @@ static void its_free_device(struct its_device 
*its_dev)
     list_del(&its_dev->entry);
     raw_spin_unlock_irqrestore(&its_dev->its->lock, flags);
     kfree(its_dev->itt);
+    kfree(its_dev->event_map.lpi_map);
+    kfree(its_dev->event_map.col_map);
     kfree(its_dev);
 }

This patch causes double free for both lpi_map and col_map in 
its_irq_domain_free():

        if (!its_dev->shared &&
            bitmap_empty(its_dev->event_map.lpi_map,
                         its_dev->event_map.nr_lpis)) {
its_lpi_free(its_dev->event_map.lpi_map, ----> 
its_dev->event_map.lpi_map is freed
                             its_dev->event_map.lpi_base,
                             its_dev->event_map.nr_lpis);
                kfree(its_dev->event_map.col_map);                ----> 
its_dev->event_map.col_map is freed

                /* Unmap device/itt */
                its_send_mapd(its_dev, 0);
                its_free_device(its_dev);                         ----> 
lpi_map and col_map are freed again
        }

Thanks,

Heyi

> Thanks,
>
> 	M.