Re: 2.6.9-rc2 hangs in posix_locks_deadlock

[Trond Myklebust <trond.myklebust@fys.uio.no>]

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På su , 19/09/2004 klokka 13:36, skreiv Vladimir B. Savkin:
> On Sun, Sep 19, 2004 at 01:32:08PM -0700, Trond Myklebust wrote:
> > P? su , 19/09/2004 klokka 13:05, skreiv Vladimir B. Savkin:
> > > > 
> > > > Today I managed to see the output of Alt+SysRq+P on the
> > > > hanged box and write down call trace (from screen, so it is incomplete).
> > > > 
> > > > EIP (c015da89) was in function posix_locks_deadlock,
> > > > and the call trace was:
> > > >  __posix_lock_file
> > > >  fcntl_setlk

Hmm...  It appears that it is indeed possible for both leases and flocks
to be on the global "blocked_list", so the appended check is *not*
redundant.
Since flocks in particular do not initialize fl_owner, I suspect that
you might be seeing wierd loops that were previously being avoided due
to the ->fl_pid checks...

Cheers,
 Trond


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[PATCH] fix posix_locks_deadlock().

"blocked_list" may contain both leases and flock locks. Since the latter in
particular do not initialize the fl_owner field, we have to beware not to
call posix_same_owner() on them.

Signed-off-by: Trond Myklebust <trond.myklebust@fys.uio.no>
---
 locks.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

Index: linux-2.6.9-rc2-up/fs/locks.c
===================================================================
--- linux-2.6.9-rc2-up.orig/fs/locks.c	2004-09-19 13:55:33.680258334 -0700
+++ linux-2.6.9-rc2-up/fs/locks.c	2004-09-19 15:37:32.595634679 -0700
@@ -634,14 +634,13 @@
 int posix_locks_deadlock(struct file_lock *caller_fl,
 				struct file_lock *block_fl)
 {
-	struct list_head *tmp;
+	struct file_lock *fl;
 
 next_task:
 	if (posix_same_owner(caller_fl, block_fl))
 		return 1;
-	list_for_each(tmp, &blocked_list) {
-		struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
-		if (posix_same_owner(fl, block_fl)) {
+	list_for_each_entry(fl, &blocked_list, fl_link) {
+		if (IS_POSIX(fl) && posix_same_owner(fl, block_fl)) {
 			fl = fl->fl_next;
 			block_fl = fl;
 			goto next_task;