[Xen-changelog] [xen-4.1-testing] x86/HPET: obtain proper lock for changing IRQ affinity

[Xen patchbot-4.1-testing <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxx>
# Date 1351497797 -3600
# Node ID 59ac9035595e6923a4e7653fd84b8c0887066ea3
# Parent  2cdf9b7338018f3d4ce8125d01564ff5587c7241
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>
xen-unstable changeset: 26063:1f4be6ee4619
xen-unstable date: Wed Oct 17 12:13:20 UTC 2012
---


diff -r 2cdf9b733801 -r 59ac9035595e xen/arch/x86/hpet.c
--- a/xen/arch/x86/hpet.c       Mon Oct 29 09:02:33 2012 +0100
+++ b/xen/arch/x86/hpet.c       Mon Oct 29 09:03:17 2012 +0100
@@ -493,6 +493,16 @@ 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);
+    desc->handler->set_affinity(ch->irq, cpumask_of_cpu(ch->cpu));
+    spin_unlock(&desc->lock);
+}
+
 static void hpet_attach_channel(int cpu, struct hpet_event_channel *ch)
 {
     ASSERT(spin_is_locked(&ch->lock));
@@ -506,9 +516,7 @@ static void hpet_attach_channel(int cpu,
     if ( ch->cpu != cpu )
         return;
 
-    /* set irq affinity */
-    irq_desc[ch->irq].handler->
-        set_affinity(ch->irq, cpumask_of_cpu(ch->cpu));
+    set_channel_irq_affinity(ch);
 }
 
 static void hpet_detach_channel(int cpu, struct hpet_event_channel *ch)
@@ -529,9 +537,7 @@ static void hpet_detach_channel(int cpu,
     }
 
     ch->cpu = first_cpu(ch->cpumask);
-    /* set irq affinity */
-    irq_desc[ch->irq].handler->
-        set_affinity(ch->irq, cpumask_of_cpu(ch->cpu));
+    set_channel_irq_affinity(ch);
 }
 
 #include <asm/mc146818rtc.h>

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