1 files changed, 85 insertions, 84 deletions

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index d972decf0324..ac222d0ab12e 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -439,8 +439,8 @@ void do_softirq(void)
 
 static LIST_HEAD(irq_hosts);
 static DEFINE_SPINLOCK(irq_big_lock);
-static DEFINE_PER_CPU(unsigned int, irq_radix_reader);
-static unsigned int irq_radix_writer;
+static unsigned int revmap_trees_allocated;
+static DEFINE_MUTEX(revmap_trees_mutex);
 struct irq_map_entry irq_map[NR_IRQS];
 static unsigned int irq_virq_count = NR_IRQS;
 static struct irq_host *irq_default_host;
@@ -583,57 +583,6 @@ void irq_set_virq_count(unsigned int count)
                 irq_virq_count = count;
 }
 
-/* radix tree not lockless safe ! we use a brlock-type mecanism
- * for now, until we can use a lockless radix tree
- */
-static void irq_radix_wrlock(unsigned long *flags)
-{
-        unsigned int cpu, ok;
-
-        spin_lock_irqsave(&irq_big_lock, *flags);
-        irq_radix_writer = 1;
-        smp_mb();
-        do {
-                barrier();
-                ok = 1;
-                for_each_possible_cpu(cpu) {
-                        if (per_cpu(irq_radix_reader, cpu)) {
-                                ok = 0;
-                                break;
-                        }
-                }
-                if (!ok)
-                        cpu_relax();
-        } while(!ok);
-}
-
-static void irq_radix_wrunlock(unsigned long flags)
-{
-        smp_wmb();
-        irq_radix_writer = 0;
-        spin_unlock_irqrestore(&irq_big_lock, flags);
-}
-
-static void irq_radix_rdlock(unsigned long *flags)
-{
-        local_irq_save(*flags);
-        __get_cpu_var(irq_radix_reader) = 1;
-        smp_mb();
-        if (likely(irq_radix_writer == 0))
-                return;
-        __get_cpu_var(irq_radix_reader) = 0;
-        smp_wmb();
-        spin_lock(&irq_big_lock);
-        __get_cpu_var(irq_radix_reader) = 1;
-        spin_unlock(&irq_big_lock);
-}
-
-static void irq_radix_rdunlock(unsigned long flags)
-{
-        __get_cpu_var(irq_radix_reader) = 0;
-        local_irq_restore(flags);
-}
-
 static int irq_setup_virq(struct irq_host *host, unsigned int virq,
                             irq_hw_number_t hwirq)
 {
@@ -788,7 +737,6 @@ void irq_dispose_mapping(unsigned int virq)
 {
         struct irq_host *host;
         irq_hw_number_t hwirq;
-        unsigned long flags;
 
         if (virq == NO_IRQ)
                 return;
@@ -821,12 +769,16 @@ void irq_dispose_mapping(unsigned int virq)
                         host->revmap_data.linear.revmap[hwirq] = NO_IRQ;
                 break;
         case IRQ_HOST_MAP_TREE:
-                /* Check if radix tree allocated yet */
-                if (host->revmap_data.tree.gfp_mask == 0)
+                /*
+                 * Check if radix tree allocated yet, if not then nothing to
+                 * remove.
+                 */
+                smp_rmb();
+                if (revmap_trees_allocated < 1)
                         break;
-                irq_radix_wrlock(&flags);
+                mutex_lock(&revmap_trees_mutex);
                 radix_tree_delete(&host->revmap_data.tree, hwirq);
-                irq_radix_wrunlock(flags);
+                mutex_unlock(&revmap_trees_mutex);
                 break;
         }
 
@@ -875,43 +827,62 @@ unsigned int irq_find_mapping(struct irq_host *host,
 EXPORT_SYMBOL_GPL(irq_find_mapping);
 
 
-unsigned int irq_radix_revmap(struct irq_host *host,
-                              irq_hw_number_t hwirq)
+unsigned int irq_radix_revmap_lookup(struct irq_host *host,
+                                     irq_hw_number_t hwirq)
 {
-        struct radix_tree_root *tree;
         struct irq_map_entry *ptr;
         unsigned int virq;
-        unsigned long flags;
 
         WARN_ON(host->revmap_type != IRQ_HOST_MAP_TREE);
 
-        /* Check if the radix tree exist yet. We test the value of
-         * the gfp_mask for that. Sneaky but saves another int in the
-         * structure. If not, we fallback to slow mode
+        /*
+         * Check if the radix tree exists and has bee initialized.
+         * If not, we fallback to slow mode
          */
-        tree = &host->revmap_data.tree;
-        if (tree->gfp_mask == 0)
+        if (revmap_trees_allocated < 2)
                 return irq_find_mapping(host, hwirq);
 
         /* Now try to resolve */
-        irq_radix_rdlock(&flags);
-        ptr = radix_tree_lookup(tree, hwirq);
-        irq_radix_rdunlock(flags);
+        /*
+         * No rcu_read_lock(ing) needed, the ptr returned can't go under us
+         * as it's referencing an entry in the static irq_map table.
+         */
+        ptr = radix_tree_lookup(&host->revmap_data.tree, hwirq);
 
-        /* Found it, return */
-        if (ptr) {
+        /*
+         * If found in radix tree, then fine.
+         * Else fallback to linear lookup - this should not happen in practice
+         * as it means that we failed to insert the node in the radix tree.
+         */
+        if (ptr)
                 virq = ptr - irq_map;
-                return virq;
-        }
+        else
+                virq = irq_find_mapping(host, hwirq);
+
+        return virq;
+}
+
+void irq_radix_revmap_insert(struct irq_host *host, unsigned int virq,
+                             irq_hw_number_t hwirq)
+{
+
+        WARN_ON(host->revmap_type != IRQ_HOST_MAP_TREE);
+
+        /*
+         * Check if the radix tree exists yet.
+         * If not, then the irq will be inserted into the tree when it gets
+         * initialized.
+         */
+        smp_rmb();
+        if (revmap_trees_allocated < 1)
+                return;
 
-        /* If not there, try to insert it */
-        virq = irq_find_mapping(host, hwirq);
         if (virq != NO_IRQ) {
-                irq_radix_wrlock(&flags);
-                radix_tree_insert(tree, hwirq, &irq_map[virq]);
-                irq_radix_wrunlock(flags);
+                mutex_lock(&revmap_trees_mutex);
+                radix_tree_insert(&host->revmap_data.tree, hwirq,
+                                  &irq_map[virq]);
+                mutex_unlock(&revmap_trees_mutex);
         }
-        return virq;
 }
 
 unsigned int irq_linear_revmap(struct irq_host *host,
@@ -1020,14 +991,44 @@ void irq_early_init(void)
 static int irq_late_init(void)
 {
         struct irq_host *h;
-        unsigned long flags;
+        unsigned int i;
 
-        irq_radix_wrlock(&flags);
+        /*
+         * No mutual exclusion with respect to accessors of the tree is needed
+         * here as the synchronization is done via the state variable
+         * revmap_trees_allocated.
+         */
         list_for_each_entry(h, &irq_hosts, link) {
                 if (h->revmap_type == IRQ_HOST_MAP_TREE)
-                        INIT_RADIX_TREE(&h->revmap_data.tree, GFP_ATOMIC);
+                        INIT_RADIX_TREE(&h->revmap_data.tree, GFP_KERNEL);
+        }
+
+        /*
+         * Make sure the radix trees inits are visible before setting
+         * the flag
+         */
+        smp_wmb();
+        revmap_trees_allocated = 1;
+
+        /*
+         * Insert the reverse mapping for those interrupts already present
+         * in irq_map[].
+         */
+        mutex_lock(&revmap_trees_mutex);
+        for (i = 0; i < irq_virq_count; i++) {
+                if (irq_map[i].host &&
+                    (irq_map[i].host->revmap_type == IRQ_HOST_MAP_TREE))
+                        radix_tree_insert(&irq_map[i].host->revmap_data.tree,
+                                          irq_map[i].hwirq, &irq_map[i]);
         }
-        irq_radix_wrunlock(flags);
+        mutex_unlock(&revmap_trees_mutex);
+
+        /*
+         * Make sure the radix trees insertions are visible before setting
+         * the flag
+         */
+        smp_wmb();
+        revmap_trees_allocated = 2;
 
         return 0;
 }