kern_yield vs ukbd_yield

[Andriy Gapon]

on 12/12/2011 21:09 Hans Petter Selasky said the following:
> On Monday 12 December 2011 20:05:38 John Baldwin wrote:
>>> Hi,
>>>
>>>
>>>
>>>> hselasky@ or someone else familiar with the various usb threads would
>>>> have to answer that.
>>>
>>>
>>>
>>> The problem is only during init() where the init thread has highest
>>> priority  and that doesn't allow other threads to run even if the
>>> scheduler is
>>
>> running!
>>
>> Hmm, that should be fixed by lowering the relevant thread's priority.
>> Do you mean thread0 (the one doing all the SYSINIT's or thread we create
>> for init (pid 1) before it executes init?
> 
> Yes, thread0. Correct!

Mmm, my short debugging session with qemu shows that it is actually pid 1:

Breakpoint 1, ukbd_do_poll (sc=0xffffff8000764000, wait=0 '\0') at
/usr/src/sys/dev/usb/input/ukbd.c:403
403     {
(kgdb) bt
#0  ukbd_do_poll (sc=0xffffff8000764000, wait=0 '\0') at
/usr/src/sys/dev/usb/input/ukbd.c:403
#1  0xffffffff803ee57e in ukbd_check (kbd=Variable "kbd" is not available.
) at /usr/src/sys/dev/usb/input/ukbd.c:1418
#2  0xffffffff803ee674 in ukbd_check_char (kbd=0xffffff8000764000) at
/usr/src/sys/dev/usb/input/ukbd.c:1450
#3  0xffffffff8035c794 in kbdmux_read_char (kbd=0xfffffe00021d2c00,
wait=Variable "wait" is not available.
) at /usr/src/sys/dev/kbdmux/kbdmux.c:665
#4  0xffffffff803bf4aa in scgetc (sc=0xffffffff81835dc0, flags=Variable "flags"
is not available.
) at /usr/src/sys/dev/syscons/syscons.c:3373
#5  0xffffffff803c2d03 in sc_cngetc (cd=Variable "cd" is not available.
) at /usr/src/sys/dev/syscons/syscons.c:1753
#6  0xffffffff804ae489 in cncheckc () at /usr/src/sys/kern/kern_cons.c:402
#7  0xffffffff804ae4c7 in cngetc () at /usr/src/sys/kern/kern_cons.c:383
#8  0xffffffff804ae9a7 in cngets (cp=0xffffff8000326aa0 "", size=80, visible=1)
at /usr/src/sys/kern/kern_cons.c:421
#9  0xffffffff80594d4e in vfs_mountroot () at /usr/src/sys/kern/vfs_mountroot.c:490
#10 0xffffffff804a6e65 in start_init (dummy=Variable "dummy" is not available.
) at /usr/src/sys/kern/init_main.c:683
#11 0xffffffff804c5a9a in fork_exit (callout=0xffffffff804a6e00 <start_init>,
arg=0x0, frame=0xffffff8000326c50) at /usr/src/sys/kern/kern_fork.c:995
#12 0xffffffff806bb72e in fork_trampoline () at
/usr/src/sys/amd64/amd64/exception.S:602
#13 0x0000000000000000 in ?? ()
(kgdb) p td->td_proc->p_pid
$7 = 1
(kgdb) p td->td_proc->p_comm
$8 = "kernel", '\0' <repeats 13 times>
(kgdb) p td->td_tid
$9 = 100002

Also:
(kgdb) p/d td->td_user_pri
$10 = 139
(kgdb) p/d td->td_base_pri
$11 = 84

-- 
Andriy Gapon