On Mon, Sep 13, 2004 at 03:25:41PM -0500, Stuart_Hayes@Dell.com wrote:
quoted text
> Michael --

Matthew, actually ...

quoted text
> It appears that samba (smbd) is getting both flocks and 
> posix locks.  Since flock_lock_file() isn't checking for 
> potential deadlocks before adding lock requests to the 
> blocked_list, we end up with (what appears to be) a circular 
> dependency between a posix lock and an flock in blocked_list.  
> This causes posix_locks_deadlock() to get stuck in a loop 
> next time we try to get a posix_lock that is blocked by 
> something with the circular dependency.
> 
> Since flocks aren't supposed to do any deadlock checking, it 
> seems like the right solution to this would be to modify 
> posix_locks_deadlock() to only check for potential deadlock 
> situations with other posix locks and lock requests, and 
> ignore flocks.

flocks aren't supposed to be on the blocked list in the first place.
I'm not sure how this hasn't been noticed before.  The correct patch
would be something like (compile-tested only):

Index: linux-2.6/fs/locks.c
===================================================================
RCS file: /var/cvs/linux-2.6/fs/locks.c,v
retrieving revision 1.12
diff -u -p -r1.12 locks.c
--- linux-2.6/fs/locks.c	13 Aug 2004 14:30:02 -0000	1.12
+++ linux-2.6/fs/locks.c	14 Sep 2004 00:54:13 -0000
@@ -459,7 +459,8 @@ static void locks_insert_block(struct fi
 	}
 	list_add_tail(&waiter->fl_block, &blocker->fl_block);
 	waiter->fl_next = blocker;
-	list_add(&waiter->fl_link, &blocked_list);
+	if (IS_POSIX(blocker))
+		list_add(&waiter->fl_link, &blocked_list);
 }
 
 /* Wake up processes blocked waiting for blocker.

-- 
"Next the statesmen will invent cheap lies, putting the blame upon 
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince 
himself that the war is just, and will thank God for the better sleep 
he enjoys after this process of grotesque self-deception." -- Mark Twain
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