Date: Wed, 14 Dec 2011 17:37:50 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Hans Petter Selasky <hselasky@c2i.net> Cc: usb@FreeBSD.org, freebsd-hackers@FreeBSD.org, John Baldwin <jhb@FreeBSD.org>, mdf@FreeBSD.org Subject: Re: kern_yield vs ukbd_yield Message-ID: <4EE8C2CE.40909@FreeBSD.org> In-Reply-To: <4EE70A1F.8040406@FreeBSD.org> References: <4EE51CB5.1060505@FreeBSD.org> <201112121658.22864.hselasky@c2i.net> <201112121405.38322.jhb@freebsd.org> <201112122009.12557.hselasky@c2i.net> <4EE67E4F.3010906@FreeBSD.org> <4EE70A1F.8040406@FreeBSD.org>
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on 13/12/2011 10:17 Andriy Gapon said the following:
> on 13/12/2011 00:21 Andriy Gapon said the following:
[snip]
> And in the view of the below data I would like us to revisit this problem.
> I looked over usb code and it seems that all usb threads are created with
> priorities of either USB_PRI_MED or USB_PRI_HIGH, which translates to
> PI_SWI(SWI_CAMBIO) and PI_SWI(SWI_NET). These priorities should be in the
> ithread range, so it's kind of surprising that the init thread (with PVM
> priority) can cause troubles for them.
So, Hans Petter, do you recall any details of this problem?
I am curious about which thread got starved by which.
BTW, given your recent improvements to pause(9) what do you think about further
extending it to also use DELAY(9) when kdb_active is set or when
SCHEDULER_STOPPED() is true? Then, probably, pause(9) could be used for both
branches in ukbd_do_poll and they could be collapsed together.
>> 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
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