Re: 2.6.21-rc7-mm2 hangs in boot (netconsole)

[Andrew Morton]

On Mon, 30 Apr 2007 17:45:55 -0700 Randy Dunlap <randy.dunlap@xxxxxxxxxx> wrote:

> Andrew Morton wrote:
> > On Mon, 30 Apr 2007 16:51:01 -0700
> > Randy Dunlap <randy.dunlap@xxxxxxxxxx> wrote:
> > 
> >> On Mon, 30 Apr 2007 08:16:53 -0700 Randy Dunlap wrote:
> >>
> >>> On Sun, 29 Apr 2007 22:23:54 -0700 Andrew Morton wrote:
> >>>
> >>>> On Sun, 29 Apr 2007 22:01:32 -0700 Randy Dunlap <randy.dunlap@xxxxxxxxxx> wrote:
> >>>>
> >>>>> On Wed, 25 Apr 2007 22:57:16 -0700 Andrew Morton wrote:
> >>>>>
> >>>>>> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc7/2.6.21-rc7-mm2/
> >>>>> I'm getting a hang near the end of booting on x86_64 UP.
> >>>>> The last initcall_debug function varies.  E.g.:
> >>>>>
> >>>>> 1/
> >>>>> [    0.140257] Calling initcall 0xffffffff806f2fa8: init_misc_binfmt+0x0/0x3f()
> >>>>> [    0.140266] initcall 0xffffffff806f2fa8: init_misc_binfmt+0x0/0x3f() returned 0.
> >>>>> [    0.140275] initcall 0xffffffff806f2fa8 ran for 0 msecs: init_misc_binfmt+0x0/0x3f()
> >>>>> [    0.140284] Calling initcall 0xffffffff806f2fe7: init_script_binfmt+0x0/0x12()
> >>>>> [    0.140293] initcall 0xffffffff806f2fe7: init_script_binfmt+0x0/0x12() returned 0.
> >>>>> [    0.140302] initcall 0xffffffff806f2fe7 ran for 0 msecs: init_script_binfmt+0x0/0x12()
> >>>>> [    0.140310] Calling initcall 0xffffffff806f2ff9: init_elf_binfmt+0x0/0x12()
> >>>>> [    0.140317] initcall 0xffffffff806f2ff9: init_elf_binfmt+0x0/0x12() returned 0.
> >>>>> [    0.140326] initcall 0xffffffff806f2ff9 ran for 0 msecs: init_elf_binfmt+0x0/0x12()
> >>>>> [    0.140335] Calling initcall 0xffffffff806f3de9: debugfs_init+0x0/0x4a()
> >>>>> [    0.140344] initcall 0xffffffff806f3de9: debugfs_init+0x0/0x4a() returned 0.
> >>>>> [    0.140351] initcall 0xffffffff806f3de9 ran for 0 msecs: debugfs_init+0x0/0x4a()
> >>>>>
> >>>>> 2/
> >>>>> [    0.140206] Calling initcall 0xffffffff806efeb1: ksysfs_init+0x0/0x29()
> >>>>> [    0.140215] initcall 0xffffffff806efeb1: ksysfs_init+0x0/0x29() returned 0.
> >>>>> [    0.140222] initcall 0xffffffff806efeb1 ran for 0 msecs: ksysfs_init+0x0/0x29()
> >>>>> [    0.140230] Calling initcall 0xffffffff806f25be: filelock_init+0x0/0x31()
> >>>>> [    0.140242] initcall 0xffffffff806f25be: filelock_init+0x0/0x31() returned 0.
> >>>>> [    0.140249] initcall 0xffffffff806f25be ran for 0 msecs: filelock_init+0x0/0x31()
> >>>>> [    0.140258] Calling initcall 0xffffffff806f2fa8: init_misc_binfmt+0x0/0x3f()
> >>>>> [    0.140266] initcall 0xffffffff806f2fa8: init_misc_binfmt+0x0/0x3f() returned 0.
> >>>>> [    0.140276] initcall 0xffffffff806f2fa8 ran for 0 msecs: init_misc_binfmt+0x0/0x3f()
> >>>>> [    0.140284] Calling initcall 0xffffffff806f2fe7: init_script_binfmt+0x0/0x12()
> >>>>> [    0.140293] initcall 0xffffffff806f2fe7: init_script_binfmt+0x0/0x12() returned 0.
> >>>>>
> >>>> So perhaps it locks during a timer interrupt.
> >>>>
> >>>>> .config is attached.
> >>>>>
> >>>>> Any ideas/suggestions?
> >>>> Just the usual: nothing from sysrq or NMI watchdog?
> >>> Nothing from either of those.  I'll jiggle some config options.
> >> config option changes didn't help, but removing
> >> 	netconsole=<params>
> >> from the kernel command line makes it all happy.  :(
> > 
> > argh.
> > 
> >> Do we know of netconsole hang problems?  (anyone?)
> > 
> > You have "time" as well?  I found on i386 uniproc that time+netconsole
> > caused hangs because the printk timestamping code was taking
> > xtime_lock for reading inside a write_seqlock.  But I though that Andi
> > fixed that.  Perhaps i386 got fixed but x86_64 did not.
> 
> Yes, I have CONFIG_PRINTK_TIME=y and disabling it allows it to boot.  Thanks.
> 
> Maybe the patch isn't merged yet?

Could be.  I don't recall whether Andi's statement was before or after
2.6.21-rc7-mm2 actually.

> Now if I can just remember this until the next time that I hit it...

Andi: unprocessor x86_64 running rc7-mm2 is hanging early in boot at
randomish times (presumably in the timer irq handler) when netconsole and
printk-time are enabled.

I was hitting the same thing on i386 uniprocessor, but I thought it got
fixed.

The problem was that the printable string which is newly passed to
mark_tsc_unstable() is printed out inside write_seqlock(xtime_lock) but
printk timestamping (and perhaps netconsole tx?) want to take xtime_lock
for reading, which will hang.

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