[patch 28/45] pdflush: handle resume wakeups

Greg KH
2006-07-17T16:32:54Z

[-- Attachment #1: pdflush-handle-resume-wakeups.patch --]
[-- Type: text/plain, Size: 2121 bytes --]

-stable review patch. If anyone has any objections, please let us know.

------------------

2.6.16 needs this. It was merged into 2.6.18-rc1 in
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d616e09ab33aa4d013a93c9b393efd5cebf78521 .

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>
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
mm/pdflush.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

--- linux-2.6.17.6.orig/mm/pdflush.c
+++ linux-2.6.17.6/mm/pdflush.c
@@ -104,21 +104,20 @@ static int __pdflush(struct pdflush_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);

--