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Subject[patch 4/4] x86/irq: Retrieve irq data after locking irq_desc
irq_data is protected by irq_desc->lock, so retrieving the irq chip
from irq_data outside the lock is racy vs. an concurrent update. Move
it into the lock held region.

While at it add a comment why the vector walk does not require
vector_lock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/kernel/irq.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

Index: tip/arch/x86/kernel/irq.c
===================================================================
--- tip.orig/arch/x86/kernel/irq.c
+++ tip/arch/x86/kernel/irq.c
@@ -497,6 +497,11 @@ void fixup_irqs(void)
*/
mdelay(1);

+ /*
+ * We can walk the vector array of this cpu without holding
+ * vector_lock because the cpu is already marked !online, so
+ * nothing else will touch it.
+ */
for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
unsigned int irr;

@@ -508,9 +513,9 @@ void fixup_irqs(void)
irq = __this_cpu_read(vector_irq[vector]);

desc = irq_to_desc(irq);
+ raw_spin_lock(&desc->lock);
data = irq_desc_get_irq_data(desc);
chip = irq_data_get_irq_chip(data);
- raw_spin_lock(&desc->lock);
if (chip->irq_retrigger) {
chip->irq_retrigger(data);
__this_cpu_write(vector_irq[vector], VECTOR_RETRIGGERED);



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