2007/6/5, Kostik Belousov <[EMAIL PROTECTED]>:
On Tue, Jun 05, 2007 at 05:43:03PM +0200, Attilio Rao wrote: > 2007/6/5, Attilio Rao <[EMAIL PROTECTED]>: > >2007/6/5, Bruce Evans <[EMAIL PROTECTED]>: > >> > >> I get a "spin lock held too long" panic during (an interrupt in?) acpi > >> initialization on booting non-PREEMPTION SCHED_4BSD SMP. Haven't tried > >> other cases. > > > >Do you have a backtrace or any other debugging stuffs available? > > Mmm, I think I got the bug. > basically, in kern_mutex.c::_mtx_unlock_sleep(), in the not-preemptive > case what happens at some point is: > > td = curthread; > if (td->td_critnest > 0 || td1->td_priority >= td->td_priority) > return; > > thread_lock(td1); > if (!TD_IS_RUNNING(td1)) { > ... > > mi_switch(SW_INVOL, NULL); > ... > } > thread_unlock(td1); > > Which is wrong beacause td1 is not curthread and really curthread > should be locked too when context switching. > > To a first look the idea is that td and td1 should be locked both, but > I just want more time to look better at it.With the following patch, I get the panic: mutex sched lock recursed at .../kern_synch.c:379 with backtrace mi_switch _mtx_unlock_sleep _mtx_unlock_flags vm_pagezero diff --git a/sys/kern/kern_mutex.c b/sys/kern/kern_mutex.c index e0592a8..bf44229 100644 --- a/sys/kern/kern_mutex.c +++ b/sys/kern/kern_mutex.c @@ -670,7 +670,9 @@ _mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line) "_mtx_unlock_sleep: %p switching out lock=%p", m, (void *)m->mtx_lock); + thread_lock(td); mi_switch(SW_INVOL, NULL); + thread_unlock(td); if (LOCK_LOG_TEST(&m->lock_object, opts)) CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p", m, (void *)m->mtx_lock);
After I back home I realized there is only sched_lock currently... not yet per-cpu locks :) So we should just disable this code for the moment (or forever). Attilio -- Peace can only be achieved by understanding - A. Einstein _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/cvs-all To unsubscribe, send any mail to "[EMAIL PROTECTED]"
