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[Xen-changelog] [xen-unstable] x86: IRQ fix incorrect logic in __clear_irq_vector

# HG changeset patch
# User Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
# Date 1313226868 -3600
# Node ID 68b903bb1b01b2a6ef9c6e8ead3be3c1c2208341
# Parent  67b883402736ef1746cd6654da4c898f70f40723
x86: IRQ fix incorrect logic in __clear_irq_vector

In the old code, tmp_mask is the cpu_and of cfg->cpu_mask and
cpu_online_map.  However, in the usual case of moving an IRQ from one
PCPU to another because the scheduler decides its a good idea,
cfg->cpu_mask and cfg->old_cpu_mask do not intersect.  This causes the
old cpu vector_irq table to keep the irq reference when it shouldn't.

This leads to a resource leak if a domain is shut down wile an irq has
a move pending, which results in Xen's create_irq() eventually failing
with -ENOSPC when all vector_irq tables are full of stale references.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

diff -r 67b883402736 -r 68b903bb1b01 xen/arch/x86/irq.c
--- a/xen/arch/x86/irq.c        Sat Aug 13 10:13:38 2011 +0100
+++ b/xen/arch/x86/irq.c        Sat Aug 13 10:14:28 2011 +0100
@@ -216,6 +216,7 @@
     if (likely(!cfg->move_in_progress))
+    cpus_and(tmp_mask, cfg->old_cpu_mask, cpu_online_map);
     for_each_cpu_mask(cpu, tmp_mask) {
         for (vector = FIRST_DYNAMIC_VECTOR; vector <= LAST_DYNAMIC_VECTOR;
                                 vector++) {

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