2008-11-20 21:09:59

by Matthew Wilcox

Subject: [PATCH] x86: Fix interrupt leak due to migration

When we migrate an interrupt from one CPU to another, we set the
move_in_progress flag and clean up the vectors later once they're not
being used. If you're unlucky and call destroy_irq() before the vectors
become un-used, the move_in_progress flag is never cleared, which causes
the interrupt to become unusable.

This was discovered by Jesse Brandeburg for whom it manifested as an
MSI-X device refusing to use MSI-X mode when the driver was unloaded
and reloaded repeatedly.

Signed-off-by: Matthew Wilcox <[email protected]>

diff --git a/arch/x86/kernel/io_apic.c b/arch/x86/kernel/io_apic.c
index 7a3f202..c9513e1 100644
--- a/arch/x86/kernel/io_apic.c
+++ b/arch/x86/kernel/io_apic.c
@@ -1140,6 +1140,20 @@ static void __clear_irq_vector(int irq)

cfg->vector = 0;
cpus_clear(cfg->domain);
+
+ if (likely(!cfg->move_in_progress))
+ return;
+ cpus_and(mask, cfg->old_domain, cpu_online_map);
+ for_each_cpu_mask_nr(cpu, mask) {
+ for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS;
+ vector++) {
+ if (per_cpu(vector_irq, cpu)[vector] != irq)
+ continue;
+ per_cpu(vector_irq, cpu)[vector] = -1;
+ break;
+ }
+ }
+ cfg->move_in_progress = 0;
}

void __setup_vector_irq(int cpu)

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."

2008-11-21 18:32:17

by Jesse Brandeburg

Subject: RE: [PATCH] x86: Fix interrupt leak due to migration

Matthew Wilcox wrote:
> When we migrate an interrupt from one CPU to another, we set the
> move_in_progress flag and clean up the vectors later once they're not
> being used. If you're unlucky and call destroy_irq() before the
> vectors become un-used, the move_in_progress flag is never cleared,
> which causes the interrupt to become unusable.
>
> This was discovered by Jesse Brandeburg for whom it manifested as an
> MSI-X device refusing to use MSI-X mode when the driver was unloaded
> and reloaded repeatedly.
>
> Signed-off-by: Matthew Wilcox <[email protected]>

We did some other quick testing on this and it seems good. Thanks
and good work Matthew!

Acked-by: Jesse Brandeburg <[email protected]>