[PATCH] uml: lock the irqs_to_free list

Fix (i.e. add some) the locking around the irqs_to_free list.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 3 deletions

diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index 4e7e3cfa21f9..bce9b3427b09 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -222,15 +222,28 @@ void enable_chan(struct line *line)
         }
 }
 
+/* Items are added in IRQ context, when free_irq can't be called, and
+ * removed in process context, when it can.
+ * This handles interrupt sources which disappear, and which need to
+ * be permanently disabled.  This is discovered in IRQ context, but
+ * the freeing of the IRQ must be done later.
+ */
+static DEFINE_SPINLOCK(irqs_to_free_lock);
 static LIST_HEAD(irqs_to_free);
 
 void free_irqs(void)
 {
         struct chan *chan;
+        LIST_HEAD(list);
+        struct list_head *ele;
+
+        spin_lock_irq(&irqs_to_free_lock);
+        list_splice_init(&irqs_to_free, &list);
+        INIT_LIST_HEAD(&irqs_to_free);
+        spin_unlock_irq(&irqs_to_free_lock);
 
-        while(!list_empty(&irqs_to_free)){
-                chan = list_entry(irqs_to_free.next, struct chan, free_list);
-                list_del(&chan->free_list);
+        list_for_each(ele, &list){
+                chan = list_entry(ele, struct chan, free_list);
 
                 if(chan->input)
                         free_irq(chan->line->driver->read_irq, chan);
@@ -246,7 +259,9 @@ static void close_one_chan(struct chan *chan, int delay_free_irq)
                 return;
 
         if(delay_free_irq){
+                spin_lock_irq(&irqs_to_free_lock);
                 list_add(&chan->free_list, &irqs_to_free);
+                spin_unlock_irq(&irqs_to_free_lock);
         }
         else {
                 if(chan->input)