Re: [uml-devel] BUG: soft lockup for a user mode linux image

["Toralf Förster" <toralf.foerster@gmx.de>]

On 10/08/2013 10:07 PM, Geert Uytterhoeven wrote:
> On Sun, Oct 6, 2013 at 11:01 PM, Toralf Förster <toralf.foerster@gmx.de> wrote:
>>> Hmm, now pages_dirtied is zero, according to the backtrace, but the BUG_ON()
>>> asserts its strict positive?!?
>>>
>>> Can you please try the following instead of the BUG_ON():
>>>
>>> if (pause < 0) {
>>>         printk("pages_dirtied = %lu\n", pages_dirtied);
>>>         printk("task_ratelimit = %lu\n", task_ratelimit);
>>>         printk("pause = %ld\n", pause);
>>> }
>>>
>>> Gr{oetje,eeting}s,
>>>
>>>                         Geert
>> I tried it in different ways already - I'm completely unsuccessful in getting any printk output.
>> As soon as the issue happens I do have a
>>
>> BUG: soft lockup - CPU#0 stuck for 22s! [trinity-child0:1521]
>>
>> at stderr of the UML and then no further input is accepted. With uml_mconsole I'm however able
>> to run very basic commands like a crash dump, sysrq ond so on.
> 
> You may get an idea of the magnitude of pages_dirtied by using a chain of
> BUG_ON()s, like:
> 
> BUG_ON(pages_dirtied > 2000000000);
> BUG_ON(pages_dirtied > 1000000000);
> BUG_ON(pages_dirtied > 100000000);
> BUG_ON(pages_dirtied > 10000000);
> BUG_ON(pages_dirtied > 1000000);
> 
> Probably 1 million is already too much for normal operation?
> 
period = HZ * pages_dirtied / task_ratelimit;
		BUG_ON(pages_dirtied > 2000000000);
		BUG_ON(pages_dirtied > 1000000000);      <-------------- this is line 1467

the back trace is :

tfoerste@n22 ~/devel/linux $ gdb --core=/mnt/ramdisk/core /home/tfoerste/devel/linux/linux -batch -ex bt
[New LWP 6911]
Core was generated by `/home/tfoerste/devel/linux/linux earlyprintk ubda=/home/tfoerste/virtual/uml/tr'.
Program terminated with signal 6, Aborted.
#0  0xb77a7424 in __kernel_vsyscall ()
#0  0xb77a7424 in __kernel_vsyscall ()
#1  0x083bdf35 in kill ()
#2  0x0807296d in uml_abort () at arch/um/os-Linux/util.c:93
#3  0x08072ca5 in os_dump_core () at arch/um/os-Linux/util.c:148
#4  0x080623c4 in panic_exit (self=0x85c1558 <panic_exit_notifier>, unused1=0, unused2=0x85f76e0 <buf.16221>) at arch/um/kernel/um_arch.c:240
#5  0x0809ba86 in notifier_call_chain (nl=0x0, val=0, v=0x85f76e0 <buf.16221>, nr_to_call=-2, nr_calls=0x0) at kernel/notifier.c:93
#6  0x0809bba1 in __atomic_notifier_call_chain (nh=0x85f76c4 <panic_notifier_list>, val=0, v=0x85f76e0 <buf.16221>, nr_to_call=0, nr_calls=0x0) at kernel/notifier.c:182
#7  0x0809bbdf in atomic_notifier_call_chain (nh=0x0, val=0, v=0x0) at kernel/notifier.c:191
#8  0x0841b5bc in panic (fmt=0x0) at kernel/panic.c:130
#9  0x0841c470 in balance_dirty_pages (pages_dirtied=23, mapping=<optimized out>) at mm/page-writeback.c:1467
#10 0x080d3595 in balance_dirty_pages_ratelimited (mapping=0x6) at mm/page-writeback.c:1661
#11 0x080e4a3f in __do_fault (mm=0x45ba3600, vma=0x48777b90, address=1084678144, pmd=0x0, pgoff=0, flags=0, orig_pte=<incomplete type>) at mm/memory.c:3452
#12 0x080e6e0f in do_linear_fault (orig_pte=..., flags=<optimized out>, pmd=<optimized out>, address=<optimized out>, vma=<optimized out>, mm=<optimized out>, page_table=<optimized out>) at mm/memory.c:3486
#13 handle_pte_fault (flags=<optimized out>, pmd=<optimized out>, pte=<optimized out>, address=<optimized out>, vma=<optimized out>, mm=<optimized out>) at mm/memory.c:3710
#14 __handle_mm_fault (flags=<optimized out>, address=<optimized out>, vma=<optimized out>, mm=<optimized out>) at mm/memory.c:3845
#15 handle_mm_fault (mm=0x45ba3600, vma=0x487034c8, address=1084678144, flags=1) at mm/memory.c:3868
#16 0x080e7817 in __get_user_pages (tsk=0x48705800, mm=0x45ba3600, start=1084678144, nr_pages=1025, gup_flags=519, pages=0x48558000, vmas=0x0, nonblocking=0x0) at mm/memory.c:1822
#17 0x080e7ae3 in get_user_pages (tsk=0x0, mm=0x0, start=0, nr_pages=0, write=1, force=0, pages=0x48777b90, vmas=0x6) at mm/memory.c:2019
#18 0x08143dc6 in aio_setup_ring (ctx=<optimized out>) at fs/aio.c:340
#19 ioctx_alloc (nr_events=<optimized out>) at fs/aio.c:605
#20 SYSC_io_setup (ctxp=<optimized out>, nr_events=<optimized out>) at fs/aio.c:1122
#21 SyS_io_setup (nr_events=65535, ctxp=135081984) at fs/aio.c:1105
#22 0x08062984 in handle_syscall (r=0x487059d4) at arch/um/kernel/skas/syscall.c:35
#23 0x08074fb5 in handle_trap (local_using_sysemu=<optimized out>, regs=<optimized out>, pid=<optimized out>) at arch/um/os-Linux/skas/process.c:198
#24 userspace (regs=0x487059d4) at arch/um/os-Linux/skas/process.c:431
#25 0x0805f750 in fork_handler () at arch/um/kernel/process.c:160
#26 0x00000000 in ?? ()



> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
> 


-- 
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3