[Linux-cluster] Re: [PATCH] suspend astd before dlm_dir_clear() in release_lockspace()

[David Teigland <teigland redhat com>]

On Fri, Mar 25, 2005 at 03:22:38PM -0800, Daniel McNeil wrote:

> Looking at the code, the problem is a race condition between
> dlm_astd() and release_lockspace().  dlm_astd can pull an
> lkb off the ast_queue and still be processing it while the
> release_lockspace() is running calls dlm_dir_clear() and
> then kfree()s ls->ls_dirtbl.  When dlm_astd() calls
> release_rsb() it leads to a dlm_dir_remove() which accesses
> the freed ls_dirtbl which is freed.  With slab debug, this
> leads a spinning write_lock() and a hung umount.  My machines
> are 2 cpu systems which also might expose the race condition.
> 
> The fix is below and is fairly simple, just do the astd_suspend()
> in release_lockspace() before the dlm_dir_clear() and kfree().
> That way astd won't be process lkb on the astqueue will it
> is being freed.

Excellent, patch applied.
Thanks

-- 
Dave Teigland  <teigland redhat com>