[PATCH] md: delay starting md threads until array is completely setup

When an array is started we start one or two threads (two if there is a
reshape or recovery that needs to be completed).

We currently start these *before* the array is completely set up and in
particular before queue->queuedata is set.  If the thread actually starts
very quickly on another CPU, we can end up dereferencing queue->queuedata
and oops.

This patch also makes sure we don't try to start a recovery if a reshape is
being restarted.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 4 insertions, 7 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9f76e0cd7805..fb50e5642c63 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3095,7 +3095,6 @@ static int do_md_run(mddev_t * mddev)
                 }
         
         set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
-        md_wakeup_thread(mddev->thread);
         
         if (mddev->sb_dirty)
                 md_update_sb(mddev);
@@ -3116,7 +3115,7 @@ static int do_md_run(mddev_t * mddev)
          * start recovery here.  If we leave it to md_check_recovery,
          * it will remove the drives and not do the right thing
          */
-        if (mddev->degraded) {
+        if (mddev->degraded && !mddev->sync_thread) {
                 struct list_head *rtmp;
                 int spares = 0;
                 ITERATE_RDEV(mddev,rdev,rtmp)
@@ -3137,10 +3136,11 @@ static int do_md_run(mddev_t * mddev)
                                        mdname(mddev));
                                 /* leave the spares where they are, it shouldn't hurt */
                                 mddev->recovery = 0;
-                        } else
-                                md_wakeup_thread(mddev->sync_thread);
+                        }
                 }
         }
+        md_wakeup_thread(mddev->thread);
+        md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
 
         mddev->changed = 1;
         md_new_event(mddev);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5764387c6989..a02f35f1a796 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3246,9 +3246,6 @@ static int run(mddev_t *mddev)
                 set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
                 mddev->sync_thread = md_register_thread(md_do_sync, mddev,
                                                         "%s_reshape");
-                /* FIXME if md_register_thread fails?? */
-                md_wakeup_thread(mddev->sync_thread);
-
         }
 
         /* read-ahead size must cover two whole stripes, which is