linux-kernel - Re: kernel 2.6.39 (user mode linux) crashes (2.6.38 works fine)

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Date:	Sat, 21 May 2011 10:53:59 +0200
From:	Toralf Förster <toralf.foerster@....de>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Darren Hart <dvhart@...ux.intel.com>,
	"richard -rw- weinberger" <richard.weinberger@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: kernel 2.6.39 (user mode linux) crashes (2.6.38 works fine)


Toralf Förster wrote at 00:53:50
> Bisecting gave :
> 
> 
> git bisect badd123375425d7df4b6081a631fc1203fceafa59b2 is the first bad
> commit commit d123375425d7df4b6081a631fc1203fceafa59b2
> Author: Thomas Gleixner <tglx@...utronix.de>
> Date:   Wed Jan 26 21:32:01 2011 +0100
> 
>     rwsem: Remove redundant asmregparm annotation
> 
>     Peter Zijlstra pointed out, that the only user of asmregparm (x86) is
>     compiling the kernel already with -mregparm=3. So the annotation of
>     the rwsem functions is redundant. Remove it.

BTW I double checked that this commit is the culprit of the hang - it is.
Furthermore I added these kernel config options :

tfoerste@n22 ~/devel/linux-2.6 $ diff .config* | grep '<' | grep -v '#'
< CONFIG_X86_CPU=y
< CONFIG_CMPXCHG_LOCAL=y
< CONFIG_IP_FIB_HASH=y
< CONFIG_RPCSEC_GSS_KRB5=y
< CONFIG_DEBUG_RT_MUTEXES=y
< CONFIG_DEBUG_PI_LIST=y
< CONFIG_DEBUG_MUTEXES=y
< CONFIG_BKL=y
< CONFIG_DEBUG_INFO=y
< CONFIG_DEBUG_WRITECOUNT=y
< CONFIG_DEBUG_LIST=y
< CONFIG_DEBUG_PAGEALLOC=y
< CONFIG_WANT_PAGE_DEBUG_FLAGS=y
< CONFIG_PAGE_POISONING=y

attached gdb to the top process of linx and run wiresahrk in parallel when I did
$>firefox https://n22_uml/phpmyadmin/ &


GDB gave :

Program received signal SIGSEGV, Segmentation fault.
0x0829f2bd in rwsem_down_failed_common (sem=0x84f6000, flags=2, adjustment=65535) at lib/rwsem.c:189
189                     adjustment += RWSEM_WAITING_BIAS;
(gdb) bt full
#0  0x0829f2bd in rwsem_down_failed_common (sem=0x84f6000, flags=2, adjustment=65535) at lib/rwsem.c:189
        waiter = {list = {next = 0x0, prev = 0x6}, task = 0x1809d480, flags = 2}
        tsk = 0x1809d480
        count = <value optimized out>
#1  0x0829f375 in rwsem_down_write_failed (sem=0x84f6000) at lib/rwsem.c:236
No locals.
#2  0x0829d0e2 in call_rwsem_down_write_failed () at arch/um/sys-i386/../../x86/lib/semaphore_32.S:97
No locals.
#3  0x0829eaa7 in __down_write_nested (sem=0x182aa774)
    at /home/tfoerste/devel/linux-2.6/arch/x86/include/asm/rwsem.h:105
        tmp = -1
#4  __down_write (sem=0x182aa774) at /home/tfoerste/devel/linux-2.6/arch/x86/include/asm/rwsem.h:121
No locals.
#5  down_write (sem=0x182aa774) at kernel/rwsem.c:51
No locals.
#6  0x080d2de3 in sys_brk (brk=139419648) at mm/mmap.c:254
        rlim = <value optimized out>
        newbrk = <value optimized out>
        oldbrk = 0
        mm = 0x182aa740
#7  0x08060d16 in handle_syscall (r=0x1809d650) at arch/um/kernel/skas/syscall.c:35
        syscall = <value optimized out>
#8  0x08074ca1 in handle_trap (regs=0x1809d650) at arch/um/os-Linux/skas/process.c:201
        err = <value optimized out>
        status = 0
#9  userspace (regs=0x1809d650) at arch/um/os-Linux/skas/process.c:417
        sig = <value optimized out>
        timer = {it_interval = {tv_sec = 0, tv_usec = 0}, it_value = {tv_sec = 0, tv_usec = 5999}}
        nsecs = <value optimized out>
        err = <value optimized out>
        status = 34175
        op = 31
        pid = 12820
        local_using_sysemu = 2
#10 0x0805e0cb in fork_handler () at arch/um/kernel/process.c:181
No locals.
#11 0xaaaaaaaa in ?? ()
No symbol table info available.
(gdb) quit


I attached the wireshark stream onto this mail - the network connections at at packet #92:

TLSv1	754	[TCP Retransmission] Change Cipher Spec, Encrypted Handshake Message, Application Data


might give a hint, that in few cases the UML system even hangs during start of the sshd, isn't it ?


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

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