Re: Processes spinning forever, apparently in lock_timer_base()?

[Chuck Ebbert <cebbert@redhat.com>]

On 09/20/2007 06:36 PM, Andrew Morton wrote:
> 
> So the question is, why do we have large amounts of dirty pages for one
> disk which appear to be sitting there not getting written?
> 
> Do we know if there's any writeout at all happening when the system is in
> this state?
> 
> I guess it's possible that the dirty inodes on the "other" disk got
> themselves onto the wrong per-sb inode list, or are on the correct list,
> but in the correct place.  If so, these:
> 
> writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists.patch
> writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-2.patch
> writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-3.patch
> writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-4.patch
> writeback-fix-comment-use-helper-function.patch
> writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-5.patch
> writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-6.patch
> writeback-fix-time-ordering-of-the-per-superblock-dirty-inode-lists-7.patch
> writeback-fix-periodic-superblock-dirty-inode-flushing.patch
> 
> from 2.6.23-rc6-mm1 should help.

Yikes! Simple fixes would be better.

Patch that is confirmed to fix the problem for this user is below, but
that one could cause other problems. I was looking for some band-aid
could be shown to be harmless...

http://lkml.org/lkml/2007/8/2/89:

------
--- linux-2.6.22.1/mm/page-writeback.c.orig	2007-07-30 16:36:09.000000000 +0100
+++ linux-2.6.22.1/mm/page-writeback.c	2007-07-31 16:26:43.000000000 +0100
@@ -250,6 +250,8 @@ static void balance_dirty_pages(struct a
 			pages_written += write_chunk - wbc.nr_to_write;
 			if (pages_written >= write_chunk)
 				break;		/* We've done our duty */
+			if (!wbc.encountered_congestion && wbc.nr_to_write > 0)
+				break;	/* didn't find enough to do */
 		}
 		congestion_wait(WRITE, HZ/10);
 	}

 
> 
> Did anyone try running /bin/sync when the system is in this state?
> 

Reporter is in the CC: list.