Re: Stop scheduler on panic

On Thursday, November 17, 2011 4:47:42 am Andriy Gapon wrote:
> on 17/11/2011 10:34 Andriy Gapon said the following:
> > on 17/11/2011 10:15 Kostik Belousov said the following:
> >> I have the following change for eons on my test boxes. Without it,
> >> I simply cannot get _any_ dump.
> >>
> >> diff --git a/sys/cam/cam_xpt.c b/sys/cam/cam_xpt.c
> >> index 10b89c7..a38e42f 100644
> >> --- a/sys/cam/cam_xpt.c
> >> +++ b/sys/cam/cam_xpt.c
> >> _at__at_ -4230,7 +4230,7 _at__at_ xpt_done(union ccb *done_ccb)
> >>  			TAILQ_INSERT_TAIL(&cam_simq, sim, links);
> >>  			mtx_unlock(&cam_simq_lock);
> >>  			sim->flags |= CAM_SIM_ON_DONEQ;
> >> -			if (first)
> >> +			if (first && panicstr == NULL)
> >>  				swi_sched(cambio_ih, 0);
> >>  		}
> >>  	}
> > 
> > I think that this (or similar) change should go into the patch and the tree.
> > 
> 
> And, BTW, I still would like to do something like the following (perhaps with
> td_oncpu = NOCPU and td_flags &= ~TDF_NEEDRESCHED also moved to the common code):
> 
> Index: sys/kern/sched_ule.c
> ===================================================================
> --- sys/kern/sched_ule.c	(revision 227608)
> +++ sys/kern/sched_ule.c	(working copy)
> _at__at_ -1790,7 +1790,6 _at__at_ sched_switch(struct thread *td, struct thread *new
>  	td->td_oncpu = NOCPU;
>  	if (!(flags & SW_PREEMPT))
>  		td->td_flags &= ~TDF_NEEDRESCHED;
> -	td->td_owepreempt = 0;
>  	tdq->tdq_switchcnt++;
>  	/*
>  	 * The lock pointer in an idle thread should never change.  Reset it
> Index: sys/kern/kern_synch.c
> ===================================================================
> --- sys/kern/kern_synch.c	(revision 227608)
> +++ sys/kern/kern_synch.c	(working copy)
> _at__at_ -406,6 +406,8 _at__at_ mi_switch(int flags, struct thread *newtd)
>  	    ("mi_switch: switch must be voluntary or involuntary"));
>  	KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
> 
> +	td->td_owepreempt = 0;
> +
>  	/*
>  	 * Don't perform context switches from the debugger.
>  	 */
> Index: sys/kern/sched_4bsd.c
> ===================================================================
> --- sys/kern/sched_4bsd.c	(revision 227608)
> +++ sys/kern/sched_4bsd.c	(working copy)
> _at__at_ -940,7 +940,6 _at__at_ sched_switch(struct thread *td, struct thread *new
>  	td->td_lastcpu = td->td_oncpu;
>  	if (!(flags & SW_PREEMPT))
>  		td->td_flags &= ~TDF_NEEDRESCHED;
> -	td->td_owepreempt = 0;
>  	td->td_oncpu = NOCPU;
> 
>  	/*
> 
> Does anybody see any potential problems with such a change?

Hmm, does this mean the preemption will be lost if you break into the
debugger and continue in the non-panic case?

-- 
John Baldwin