[Xen-changelog] [xen-unstable] x86/HPET: obtain proper lock for changing IRQ affinity

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxx>
# Date 1350476000 -7200
# Node ID 1f4be6ee4619c88c273cb457d8e7f1eee49d00dd
# Parent  ec8a091efcce717584b00ce76e3cec40a6247ebc
x86/HPET: obtain proper lock for changing IRQ affinity

The IRQ descriptor lock should be held while adjusting the affinity of
any IRQ; the HPET channel lock isn't sufficient to protect namely
against races with moving the IRQ to a different CPU.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Keir Fraser <keir@xxxxxxx>
---


diff -r ec8a091efcce -r 1f4be6ee4619 xen/arch/x86/hpet.c
--- a/xen/arch/x86/hpet.c       Wed Oct 17 14:12:06 2012 +0200
+++ b/xen/arch/x86/hpet.c       Wed Oct 17 14:13:20 2012 +0200
@@ -436,6 +436,16 @@ static struct hpet_event_channel *hpet_g
     return ch;
 }
 
+static void set_channel_irq_affinity(const struct hpet_event_channel *ch)
+{
+    struct irq_desc *desc = irq_to_desc(ch->irq);
+
+    ASSERT(!local_irq_is_enabled());
+    spin_lock(&desc->lock);
+    hpet_msi_set_affinity(desc, cpumask_of(ch->cpu));
+    spin_unlock(&desc->lock);
+}
+
 static void hpet_attach_channel(unsigned int cpu,
                                 struct hpet_event_channel *ch)
 {
@@ -450,7 +460,7 @@ static void hpet_attach_channel(unsigned
     if ( ch->cpu != cpu )
         return;
 
-    hpet_msi_set_affinity(irq_to_desc(ch->irq), cpumask_of(ch->cpu));
+    set_channel_irq_affinity(ch);
 }
 
 static void hpet_detach_channel(unsigned int cpu,
@@ -472,7 +482,7 @@ static void hpet_detach_channel(unsigned
     }
 
     ch->cpu = cpumask_first(ch->cpumask);
-    hpet_msi_set_affinity(irq_to_desc(ch->irq), cpumask_of(ch->cpu));
+    set_channel_irq_affinity(ch);
 }
 
 #include <asm/mc146818rtc.h>

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