On Tue, Mar 29, 2005 at 04:04:46PM -0500, der Mouse wrote:
> A 2.0 machine at work has been wedging recently.  This time I spent
> some time poking at it with ddb, and after chasing through "proc P1 is
> blocking on lock L1, which is held by P2, who is blocking on L2, which
> is held by...", I wound up at a process that was blocked in a call
> chain that went sys_open, vn_open, ufs_setattr, ffs_truncate,
> ffs_update, bwrite, biowait, ltsleep.  I looked at the buffer passed to
> bwrite/biowait, and it showed flags=CACHE|SCANNED|BUSY, dev=0x80001300.
> The dev is slightly odd, because the high bit of the minor number is
> set for no visible reason.  (The machine does in fact have root on
> ld0a, but /dev/ld0a has minor 0, not 0x80000.)
> 
> But the real oddity is that the buffer has b_bufsize=b_bcount=0x2000,
> but b_resid=0x258f.  Is it as wrong as it looks for b_resid to be
> higher than b_bcount like this, or is there just something I'm not
> understanding here?

b_resid is abused to store b_cylinder. This is done by bound_check_with_label()
and is used by the sort algorithm. So if it is sitting in the
disk's queue, it shoukd be OK.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--