Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754580Ab3JISn7 (ORCPT ); Wed, 9 Oct 2013 14:43:59 -0400 Received: from b.ns.miles-group.at ([95.130.255.144]:1660 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751854Ab3JISn6 (ORCPT ); Wed, 9 Oct 2013 14:43:58 -0400 Message-ID: <5255A3E6.6020100@nod.at> Date: Wed, 09 Oct 2013 20:43:50 +0200 From: Richard Weinberger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130620 Thunderbird/17.0.7 MIME-Version: 1.0 To: =?UTF-8?B?VG9yYWxmIEbDtnJzdGVy?= CC: Geert Uytterhoeven , UML devel , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , Jan Kara , hannes@cmpxchg.org, darrick.wong@oracle.com, Michal Hocko Subject: Re: [uml-devel] BUG: soft lockup for a user mode linux image References: <524C6643.2040209@gmx.de> <524DBD5D.1040203@gmx.de> <524DBFBB.1050002@nod.at> <524DC278.3020106@gmx.de> <524DC394.6030406@nod.at> <524DC675.4020201@gmx.de> <524E57BA.805@nod.at> <52517109.90605@gmx.de> <5251C334.3010604@gmx.de> <5251CF94.5040101@gmx.de> <525591AD.4060401@gmx.de> In-Reply-To: <525591AD.4060401@gmx.de> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5800 Lines: 116 CC'ing mm folks. Please see below. Am 09.10.2013 19:26, schrieb Toralf Förster: > On 10/08/2013 10:07 PM, Geert Uytterhoeven wrote: >> On Sun, Oct 6, 2013 at 11:01 PM, Toralf Förster 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 Summary for mm people: Toralf runs trinty on UML/i386. After some time pages_dirtied becomes very large. More than 1000000000 pages in this case. Thus, period = HZ * pages_dirtied / task_ratelimit overflows and period/pause becomes extremely large. It looks like io_schedule_timeout() get's called with a very large timeout. I don't know why "if (unlikely(pause > max_pause)) {" does not help. Any ideas? Thanks, //richard > 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 , unused1=0, unused2=0x85f76e0 ) at arch/um/kernel/um_arch.c:240 > #5 0x0809ba86 in notifier_call_chain (nl=0x0, val=0, v=0x85f76e0 , nr_to_call=-2, nr_calls=0x0) at kernel/notifier.c:93 > #6 0x0809bba1 in __atomic_notifier_call_chain (nh=0x85f76c4 , val=0, v=0x85f76e0 , 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=) 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=) at mm/memory.c:3452 > #12 0x080e6e0f in do_linear_fault (orig_pte=..., flags=, pmd=, address=, vma=, mm=, page_table=) at mm/memory.c:3486 > #13 handle_pte_fault (flags=, pmd=, pte=, address=, vma=, mm=) at mm/memory.c:3710 > #14 __handle_mm_fault (flags=, address=, vma=, mm=) 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=) at fs/aio.c:340 > #19 ioctx_alloc (nr_events=) at fs/aio.c:605 > #20 SYSC_io_setup (ctxp=, nr_events=) 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=, regs=, pid=) 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 >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/