Re: schedcpu() in /sys/kern/sched_4bsd.c calls thread_lock() on thread with un-initialized td_lock

On Thu, Mar 31, 2011 at 3:58 PM, John Baldwin <jhb_at_freebsd.org> wrote:
> On Thursday, March 31, 2011 7:32:26 am Svatopluk Kraus wrote:
>> Hi,
>>
>>   I've got a page fault (because of NULL td_lock) in
>> thread_lock_flags() called from schedcpu() in /sys/kern/sched_4bsd.c
>> file. During process fork, new thread is linked to new process which
>> is linked to allproc list and both allproc_lock and new process lock
>> are unlocked before sched_fork() is called, where new thread td_lock
>> is initialized. Only PRS_NEW process status is on sentry but not
>> checked in schedcpu().
>
> I think this should fix it:
>
> Index: sched_4bsd.c
> ===================================================================
> --- sched_4bsd.c        (revision 220190)
> +++ sched_4bsd.c        (working copy)
> _at__at_ -463,6 +463,10 _at__at_ schedcpu(void)
>        sx_slock(&allproc_lock);
>        FOREACH_PROC_IN_SYSTEM(p) {
>                PROC_LOCK(p);
> +               if (p->p_state == PRS_NEW) {
> +                       PROC_UNLOCK(p);
> +                       continue;
> +               }
>                FOREACH_THREAD_IN_PROC(p, td) {
>                        awake = 0;
>                        thread_lock(td);
>

Thanks for patch. Maybe, test p_state not to be PRS_NORMAL could be better?

I've got next (same reason) page fault in thread_lock_flags() called
from scheduler() in sys/vm/vm_glue.c. I try to search for
FOREACH_THREAD_IN_PROC() together with FOREACH_PROC_IN_SYSTEM() in
/sys subtree and next problem could be in deadlkres() in
sys/kern/kern_clock.c at least.