[PATCH] pdflush: handle resume wakeups

pdflush is carefully designed to ensure that all wakeups have some
corresponding work to do - if a woken-up pdflush thread discovers that it
hasn't been given any work to do then this is considered an error.

That all broke when swsusp came along - because a timer-delivered wakeup to a
frozen pdflush thread will just get lost.  This causes the pdflush thread to
get lost as well: the writeback timer is supposed to be re-armed by pdflush in
process context, but pdflush doesn't execute the callout which does this.

Fix that up by ignoring the return value from try_to_freeze(): jsut proceed,
see if we have any work pending and only go back to sleep if that is not the
case.

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

1 files changed, 7 insertions, 8 deletions

diff --git a/mm/pdflush.c b/mm/pdflush.c
index df7e50b8f70c..b02102feeb4b 100644
--- a/mm/pdflush.c
+++ b/mm/pdflush.c
@@ -104,21 +104,20 @@ static int __pdflush(struct pdflush_work *my_work)
                 list_move(&my_work->list, &pdflush_list);
                 my_work->when_i_went_to_sleep = jiffies;
                 spin_unlock_irq(&pdflush_lock);
-
                 schedule();
-                if (try_to_freeze()) {
-                        spin_lock_irq(&pdflush_lock);
-                        continue;
-                }
-
+                try_to_freeze();
                 spin_lock_irq(&pdflush_lock);
                 if (!list_empty(&my_work->list)) {
-                        printk("pdflush: bogus wakeup!\n");
+                        /*
+                         * Someone woke us up, but without removing our control
+                         * structure from the global list.  swsusp will do this
+                         * in try_to_freeze()->refrigerator().  Handle it.
+                         */
                         my_work->fn = NULL;
                         continue;
                 }
                 if (my_work->fn == NULL) {
-                        printk("pdflush: NULL work function\n");
+                        printk("pdflush: bogus wakeup\n");
                         continue;
                 }
                 spin_unlock_irq(&pdflush_lock);