genirq: Prevent proc race against freeing of irq descriptors

[cascardo/linux.git] / kernel / irq / irqdesc.c

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index a1782f8..99793b9 100644 (file)
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -132,6 +132,16 @@ 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;
@@ -168,6 +178,12 @@ 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);
@@ -574,6 +590,15 @@ void kstat_incr_irq_this_cpu(unsigned int irq)
        kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));
 }
 
+/**
+ * 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);
@@ -582,6 +607,14 @@ 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);
@@ -594,3 +627,22 @@ 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;
+}