genirq: keep affinities set from userspace across free/request_irq()

Impact: preserve user-modified affinities on interrupts

Kumar Galak noticed that commit
18404756765c713a0be4eb1082920c04822ce588 (genirq: Expose default irq
affinity mask (take 3))

overrides an already set affinity setting across a free /
request_irq(). Happens e.g. with ifdown/ifup of a network device.

Change the logic to mark the affinities as set and keep them
intact. This also fixes the unlocked access to irq_desc in
irq_select_affinity() when called from irq_affinity_proc_write()

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 48 insertions, 10 deletions

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index c498a1b8c621..634a2a955104 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -82,24 +82,27 @@ int irq_can_set_affinity(unsigned int irq)
 int irq_set_affinity(unsigned int irq, cpumask_t cpumask)
 {
         struct irq_desc *desc = irq_to_desc(irq);
+        unsigned long flags;
 
         if (!desc->chip->set_affinity)
                 return -EINVAL;
 
+        spin_lock_irqsave(&desc->lock, flags);
+
 #ifdef CONFIG_GENERIC_PENDING_IRQ
         if (desc->status & IRQ_MOVE_PCNTXT || desc->status & IRQ_DISABLED) {
-                unsigned long flags;
-
-                spin_lock_irqsave(&desc->lock, flags);
                 desc->affinity = cpumask;
                 desc->chip->set_affinity(irq, cpumask);
-                spin_unlock_irqrestore(&desc->lock, flags);
-        } else
-                set_pending_irq(irq, cpumask);
+        } else {
+                desc->status |= IRQ_MOVE_PENDING;
+                desc->pending_mask = cpumask;
+        }
 #else
         desc->affinity = cpumask;
         desc->chip->set_affinity(irq, cpumask);
 #endif
+        desc->status |= IRQ_AFFINITY_SET;
+        spin_unlock_irqrestore(&desc->lock, flags);
         return 0;
 }
 
@@ -107,24 +110,59 @@ int irq_set_affinity(unsigned int irq, cpumask_t cpumask)
 /*
  * Generic version of the affinity autoselector.
  */
-int irq_select_affinity(unsigned int irq)
+int do_irq_select_affinity(unsigned int irq, struct irq_desc *desc)
 {
         cpumask_t mask;
-        struct irq_desc *desc;
 
         if (!irq_can_set_affinity(irq))
                 return 0;
 
         cpus_and(mask, cpu_online_map, irq_default_affinity);
 
-        desc = irq_to_desc(irq);
+        /*
+         * Preserve an userspace affinity setup, but make sure that
+         * one of the targets is online.
+         */
+        if (desc->status & IRQ_AFFINITY_SET) {
+                if (cpus_intersects(desc->affinity, cpu_online_map))
+                        mask = desc->affinity;
+                else
+                        desc->status &= ~IRQ_AFFINITY_SET;
+        }
+
         desc->affinity = mask;
         desc->chip->set_affinity(irq, mask);
 
         return 0;
 }
+#else
+static inline int do_irq_select_affinity(unsigned int irq, struct irq_desc *d)
+{
+        return irq_select_affinity(irq);
+}
 #endif
 
+/*
+ * Called when affinity is set via /proc/irq
+ */
+int irq_select_affinity_usr(unsigned int irq)
+{
+        struct irq_desc *desc = irq_to_desc(irq);
+        unsigned long flags;
+        int ret;
+
+        spin_lock_irqsave(&desc->lock, flags);
+        ret = do_irq_select_affinity(irq, desc);
+        spin_unlock_irqrestore(&desc->lock, flags);
+
+        return ret;
+}
+
+#else
+static inline int do_select_irq_affinity(int irq, struct irq_desc *desc)
+{
+        return 0;
+}
 #endif
 
 /**
@@ -446,7 +484,7 @@ __setup_irq(unsigned int irq, struct irq_desc * desc, struct irqaction *new)
                         desc->depth = 1;
 
                 /* Set default affinity mask once everything is setup */
-                irq_select_affinity(irq);
+                do_irq_select_affinity(irq, desc);
 
         } else if ((new->flags & IRQF_TRIGGER_MASK)
                         && (new->flags & IRQF_TRIGGER_MASK)