async: fix __lowest_in_progress()

At 37000 feet somewhere near Greenland I woke up from a half-sleep with the
realisation that __lowest_in_progress() is buggy. After landing I checked
and there were indeed 2 problems with it; this patch fixes both:
* The order of the list checks was wrong
* The locking was not correct.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 5 deletions

diff --git a/kernel/async.c b/kernel/async.c
index f286e9f2b736..608b32b42812 100644
--- a/kernel/async.c
+++ b/kernel/async.c
@@ -90,12 +90,12 @@ extern int initcall_debug;
 static async_cookie_t  __lowest_in_progress(struct list_head *running)
 {
         struct async_entry *entry;
-        if (!list_empty(&async_pending)) {
-                entry = list_first_entry(&async_pending,
+        if (!list_empty(running)) {
+                entry = list_first_entry(running,
                         struct async_entry, list);
                 return entry->cookie;
-        } else if (!list_empty(running)) {
-                entry = list_first_entry(running,
+        } else if (!list_empty(&async_pending)) {
+                entry = list_first_entry(&async_pending,
                         struct async_entry, list);
                 return entry->cookie;
         } else {
@@ -104,6 +104,17 @@ static async_cookie_t  __lowest_in_progress(struct list_head *running)
         }
 
 }
+
+static async_cookie_t  lowest_in_progress(struct list_head *running)
+{
+        unsigned long flags;
+        async_cookie_t ret;
+
+        spin_lock_irqsave(&async_lock, flags);
+        ret = __lowest_in_progress(running);
+        spin_unlock_irqrestore(&async_lock, flags);
+        return ret;
+}
 /*
  * pick the first pending entry and run it
  */
@@ -229,7 +240,7 @@ void async_synchronize_cookie_special(async_cookie_t cookie, struct list_head *r
                 starttime = ktime_get();
         }
 
-        wait_event(async_done, __lowest_in_progress(running) >= cookie);
+        wait_event(async_done, lowest_in_progress(running) >= cookie);
 
         if (initcall_debug && system_state == SYSTEM_BOOTING) {
                 endtime = ktime_get();