linux-kernel - Re: [BUG] uml panics with "Segfault with no mm" in v3.19-rc

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Date:	Wed, 10 Dec 2014 11:49:23 +0100
From:	Richard Weinberger <richard@....at>
To:	Miklos Szeredi <miklos@...redi.hu>
CC:	Ley Foon Tan <lftan@...era.com>, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org, Daniel Walter <sahne@...0.at>,
	user-mode-linux-devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: Re: [BUG] uml panics with "Segfault with no mm" in v3.19-rc

Hi!

Am 10.12.2014 um 11:46 schrieb Miklos Szeredi:
> The guilty commit is:
> 
>   00f634bc522d "asm-generic: add generic futex for !CONFIG_SMP"

Thanks a lot Miklos!
Your bisecting faster than I do.

Let's dig into the issue!

Thanks,
//richard

> And the backtrace:
> 
> #0  0x00007ffff7866457 in kill () from /lib64/libc.so.6
> #1  0x000000006002a454 in uml_abort () at arch/um/os-Linux/util.c:93
> #2  0x000000006002a7e5 in os_dump_core () at arch/um/os-Linux/util.c:148
> #3  0x000000006001b48a in panic_exit (self=<optimized out>, unused1=<optimized out>, unused2=<optimized out>) at arch/um/kernel/um_arch.c:240
> #4  0x000000006004e4df in notifier_call_chain (nl=<optimized out>, val=6, v=0xffffffff, nr_to_call=-1, nr_calls=0x0) at kernel/notifier.c:93
> #5  0x000000006004e558 in __atomic_notifier_call_chain (nr_calls=<optimized out>, nr_to_call=<optimized out>, v=<optimized out>, val=<optimized out>, nh=<optimized out>) at kernel/notifier.c:183
> #6  atomic_notifier_call_chain (nh=<optimized out>, val=<optimized out>, v=<optimized out>) at kernel/notifier.c:193
> #7  0x0000000060238570 in panic (fmt=<optimized out>) at kernel/panic.c:133
> #8  0x000000006001ad91 in segv (fi=..., ip=1610803493, is_user=<optimized out>, regs=0x602c1840 <cpu0_irqstack+6208>) at arch/um/kernel/trap.c:218
> #9  0x000000006001b0f8 in segv_handler (sig=<optimized out>, unused_si=<optimized out>, regs=<optimized out>) at arch/um/kernel/trap.c:191
> #10 0x0000000060029238 in sig_handler_common (sig=11, si=0x602c1d30 <cpu0_irqstack+7472>, mc=<optimized out>) at arch/um/os-Linux/signal.c:44
> #11 0x0000000060029304 in sig_handler (sig=<optimized out>, si=<optimized out>, mc=<optimized out>) at arch/um/os-Linux/signal.c:231
> #12 0x0000000060028dfd in hard_handler (sig=<optimized out>, si=0x6, p=<optimized out>) at arch/um/os-Linux/signal.c:165
> #13 <signal handler called>
> #14 memcpy () at arch/x86/um/../lib/memcpy_64.S:160
> #15 0x000000006001c13d in copy_from_user (to=0x61c49e28, from=<optimized out>, n=<optimized out>) at arch/um/kernel/skas/uaccess.c:145
> #16 0x0000000060072618 in futex_atomic_cmpxchg_inatomic (newval=<optimized out>, oldval=<optimized out>, uaddr=<optimized out>, uval=<optimized out>) at include/asm-generic/futex.h:109
> #17 cmpxchg_futex_value_locked (curval=0x61c49e28, uaddr=0x0, uval=<optimized out>, newval=<optimized out>) at kernel/futex.c:596
> #18 0x0000000060008b70 in futex_detect_cmpxchg () at kernel/futex.c:3020
> #19 futex_init () at kernel/futex.c:3043
> #20 0x00000000600166ba in do_one_initcall (fn=0x60008adf <futex_init>) at init/main.c:791
> 
> Thanks,
> Miklos
> 
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