Date: Wed, 11 Sep 2002 06:18:48 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: Robert Watson <rwatson@FreeBSD.ORG> Cc: Don Lewis <dl-freebsd@catspoiler.org>, <current@FreeBSD.ORG>, <jeff@FreeBSD.ORG> Subject: Re: vnode lock assertion problem in nfs_link() Message-ID: <20020911060453.C3443-100000@gamplex.bde.org> In-Reply-To: <Pine.NEB.3.96L.1020910153259.95428D-100000@fledge.watson.org>
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On Tue, 10 Sep 2002, Robert Watson wrote:
> ... Also, last time I tried to use the ddb
> show lockedvnods command, I got the problem attached below due to locking
> issues, which makes it a lot harder to debug locking problems...
>
> Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
> robert@fledge.watson.org Network Associates Laboratories
>
> db> show lockedvnods
> Locked vnodes
> panic: blockable sleep lock (sleep mutex) mountlist @
> ../../../kern/vfs_subr.c:2621
> Debugger("panic")
Try removing all the locking in the command. ddb commands can't use locking.
I have printfs in _mtx_lock_flags(), _mtx_lock_spin_flags(),
_mtx_lock_sleep() and _mtx_lock_spin() to detect locking when ddb is active.
The error handling would be better if trap_fatal() were called before panic
panic(), like it is for null pointer panics. ddb on i386's then notices
that it shot itself and longjmps to its entry point. This handles things
like reading through garbage pointers OK, but not external state changes
like locking. Maybe my printfs should be trap_fatals or or direct longjmps.
Bruce
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