on 17/11/2011 18:37 John Baldwin said the following:
> 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
>>>> @@ -4230,7 +4230,7 @@ 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)
>> @@ -1790,7 +1790,6 @@ 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)
>> @@ -406,6 +406,8 @@ 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)
>> @@ -940,7 +940,6 @@ 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?
Not sure which exact scenario you have in mind.
Please note that the above diff just moves resetting of td_owepreempt to an
earlier place. As far as I can see there are no checks of td_owepreempt value
between the new place and the old places.
--
Andriy Gapon
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