genirq: Prevent proc race against freeing of irq descriptors

[pandora-kernel.git] / kernel / irq / irqdesc.c

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 1550e84..f497ff7 100644 (file)
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -9,7 +9,7 @@
  */
 #include <linux/irq.h>
 #include <linux/slab.h>
-#include <linux/module.h>
+#include <linux/export.h>
 #include <linux/interrupt.h>
 #include <linux/kernel_stat.h>
 #include <linux/radix-tree.h>
@@ -130,6 +130,16 @@ static void free_masks(struct irq_desc *desc)
 static inline void free_masks(struct irq_desc *desc) { }
 #endif
 
+void irq_lock_sparse(void)
+{
+       mutex_lock(&sparse_irq_lock);
+}
+
+void irq_unlock_sparse(void)
+{
+       mutex_unlock(&sparse_irq_lock);
+}
+
 static struct irq_desc *alloc_desc(int irq, int node, struct module *owner)
 {
        struct irq_desc *desc;
@@ -166,6 +176,12 @@ static void free_desc(unsigned int irq)
 
        unregister_irq_proc(irq, desc);
 
+       /*
+        * sparse_irq_lock protects also show_interrupts() and
+        * kstat_irq_usr(). Once we deleted the descriptor from the
+        * sparse tree we can free it. Access in proc will fail to
+        * lookup the descriptor.
+        */
        mutex_lock(&sparse_irq_lock);
        delete_irq_desc(irq);
        mutex_unlock(&sparse_irq_lock);
@@ -487,6 +503,15 @@ void dynamic_irq_cleanup(unsigned int irq)
        raw_spin_unlock_irqrestore(&desc->lock, flags);
 }
 
+/**
+ * kstat_irqs_cpu - Get the statistics for an interrupt on a cpu
+ * @irq:       The interrupt number
+ * @cpu:       The cpu number
+ *
+ * Returns the sum of interrupt counts on @cpu since boot for
+ * @irq. The caller must ensure that the interrupt is not removed
+ * concurrently.
+ */
 unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
 {
        struct irq_desc *desc = irq_to_desc(irq);
@@ -495,6 +520,14 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
                        *per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
 }
 
+/**
+ * kstat_irqs - Get the statistics for an interrupt
+ * @irq:       The interrupt number
+ *
+ * Returns the sum of interrupt counts on all cpus since boot for
+ * @irq. The caller must ensure that the interrupt is not removed
+ * concurrently.
+ */
 unsigned int kstat_irqs(unsigned int irq)
 {
        struct irq_desc *desc = irq_to_desc(irq);
@@ -507,3 +540,22 @@ unsigned int kstat_irqs(unsigned int irq)
                sum += *per_cpu_ptr(desc->kstat_irqs, cpu);
        return sum;
 }
+
+/**
+ * kstat_irqs_usr - Get the statistics for an interrupt
+ * @irq:       The interrupt number
+ *
+ * Returns the sum of interrupt counts on all cpus since boot for
+ * @irq. Contrary to kstat_irqs() this can be called from any
+ * preemptible context. It's protected against concurrent removal of
+ * an interrupt descriptor when sparse irqs are enabled.
+ */
+unsigned int kstat_irqs_usr(unsigned int irq)
+{
+       int sum;
+
+       irq_lock_sparse();
+       sum = kstat_irqs(irq);
+       irq_unlock_sparse();
+       return sum;
+}