Re: [Bug 18632] "INFO: task" dpkg "blocked for more than 120 seconds.

[Christoph Hellwig <hch@infradead.org>]

On Fri, Jun 10, 2011 at 11:21:49AM +0800, Wu Fengguang wrote:
> > Can you check if that helps with your livelock test case?  (And yes, I
> > should go and try it myself.  Will do as soon as I'll get a bit more
> > time).
> 
> My pleasure. It's easier to compare results on the same test bed and
> I've made it very convenient to test patches :)

Here's one that should be even better, although in it's current form it
break a subtile corner case of sync semantics, so it'll need more work
if I go down that way:

Index: xfs/fs/xfs/linux-2.6/xfs_sync.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_sync.c	2011-06-17 14:16:18.442399481 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_sync.c	2011-06-18 17:55:44.864025123 +0200
@@ -359,14 +359,16 @@ xfs_quiesce_data(
 {
 	int			error, error2 = 0;
 
-	/* push non-blocking */
-	xfs_sync_data(mp, 0);
 	xfs_qm_sync(mp, SYNC_TRYLOCK);
-
-	/* push and block till complete */
-	xfs_sync_data(mp, SYNC_WAIT);
 	xfs_qm_sync(mp, SYNC_WAIT);
 
+	/* flush all pending size updates and unwritten extent conversions */
+	flush_workqueue(xfsconvertd_workqueue);
+	flush_workqueue(xfsdatad_workqueue);
+
+	/* force out the newly dirtied log buffers */
+	xfs_log_force(mp, XFS_LOG_SYNC);
+
 	/* write superblock and hoover up shutdown errors */
 	error = xfs_sync_fsdata(mp);
 
Index: xfs/fs/xfs/linux-2.6/xfs_super.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_super.c	2011-06-18 17:51:05.660705925 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_super.c	2011-06-18 17:52:50.107367305 +0200
@@ -929,45 +929,12 @@ xfs_fs_write_inode(
 		 * ->sync_fs call do that for thus, which reduces the number
 		 * of synchronous log foces dramatically.
 		 */
-		xfs_ioend_wait(ip);
 		xfs_ilock(ip, XFS_ILOCK_SHARED);
-		if (ip->i_update_core) {
+		if (ip->i_update_core)
 			error = xfs_log_inode(ip);
-			if (error)
-				goto out_unlock;
-		}
-	} else {
-		/*
-		 * We make this non-blocking if the inode is contended, return
-		 * EAGAIN to indicate to the caller that they did not succeed.
-		 * This prevents the flush path from blocking on inodes inside
-		 * another operation right now, they get caught later by
-		 * xfs_sync.
-		 */
-		if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED))
-			goto out;
-
-		if (xfs_ipincount(ip) || !xfs_iflock_nowait(ip))
-			goto out_unlock;
-
-		/*
-		 * Now we have the flush lock and the inode is not pinned, we
-		 * can check if the inode is really clean as we know that
-		 * there are no pending transaction completions, it is not
-		 * waiting on the delayed write queue and there is no IO in
-		 * progress.
-		 */
-		if (xfs_inode_clean(ip)) {
-			xfs_ifunlock(ip);
-			error = 0;
-			goto out_unlock;
-		}
-		error = xfs_iflush(ip, SYNC_TRYLOCK);
+		xfs_iunlock(ip, XFS_ILOCK_SHARED);
 	}
 
- out_unlock:
-	xfs_iunlock(ip, XFS_ILOCK_SHARED);
- out:
 	/*
 	 * if we failed to write out the inode then mark
 	 * it dirty again so we'll try again later.