Date: Thu, 7 Mar 2002 04:34:00 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: <qhwt@myrealbox.com> Cc: <current@FreeBSD.ORG> Subject: Re: Won't boot after the commits to timecounter code Message-ID: <20020307040247.T9712-100000@gamplex.bde.org> In-Reply-To: <20020306134746.GA342@gzl>
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On Wed, 6 Mar 2002 qhwt@myrealbox.com wrote:
> I inserted a pair of printf() inside mtx_lock_spin/mtx_unlock_spin in
> i8254_get_timecount() and it kept printing the message while tc_init()
> was blocked, so I think it's blocked at mtx_lock_spin in i8254_get_timecount()
> when called from tc_init(), but not when called from somewhere else.
> (maybe an interrupt handler?)
Apparently you have KTR enabled (not the default in GENERIC). I think
WITNESS+KTR already caused nasty recursion from the mtx_lock_spin, and
we now get an endless loop when nanotime() is called with an invalid
timecounter in the following call chain:
tc_init -> tc_windup -> tco_delta -> i8254_get_timecount -> mtx_foo ->
witness_foo -> ktr_foo -> nanotime,
just after nanotime has somehow recursed back into i8254_get_timecounter
without causing endless recursion!
Try setting MTX_NOWITNESS in the initialization of clock_lock in
i386/machdep.c.
Bruce
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