[uml-devel] Kernel panic "read of switch_pipe failed" in 2.6.8.1

[uml-devel] Kernel panic "read of switch_pipe failed" in 2.6.8.1

[Lars Kellogg-Stedman]

I'm occasionally seeing the following during the UML boot process:

  Kernel panic: read of switch_pipe failed, errno = 9

At which point UML hangs after printing out a call trace.

I'm starting UML like this:

  linux umid=uml1 ubd0=/tmp/root_fs \
    con0=fd:0,fd:1 con=port:9001 eth0=mcast

Has anyone seen this behavior?  It's not happening frequently -- for 
example, I've restarted UML several times while typing this message in 
an attempt to capture the call trace without triggering the panic.

-- Lars



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Re: [uml-devel] Kernel panic "read of switch_pipe failed" in 2.6.8.1

[Jeff Dike]

lars@oddbit.com said:
> I'm occasionally seeing the following during the UML boot process:
>   Kernel panic: read of switch_pipe failed, errno = 9 

What's the full output?

This has happened once or twice before, and the cause was something closing
the wrong file descriptor.

				Jeff



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[uml-devel] Re: Kernel panic "read of switch_pipe failed" in 2.6.8.1

[Lars Kellogg-Stedman]

In article <200410122333.i9CNXq3P004254@ccure.user-mode-linux.org>,
 Jeff Dike <jdike@addtoit.com> wrote:

> What's the full output?
> 
> This has happened once or twice before, and the cause was something closing
> the wrong file descriptor.

Here's the complete kernel log:

Checking for the skas3 patch in the host...not found
Checking for /proc/mm...not found
tracing thread pid = 10637
Linux version 2.6.8.1-1um (lars@flowers) (gcc version 3.3.4 (Debian 
1:3.3.4-13)) #1 Mon Oct 11 11:34:18 EDT 2004
Built 1 zonelists
Kernel command line: uml_dir=/var/uml/machines/lars000/control 
ubd0=root_fs.cow mem=64m con0=fd:0,fd:1 con=null umlctl=ssl4 ssl4=pts 
root=98:0
PID hash table entries: 16 (order 4: 128 bytes)
Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
Memory: 60848k available
Calibrating delay loop... 313.75 BogoMIPS
Mount-cache hash table entries: 512 (order: 0, 4096 bytes)
Checking for host processor cmov support...Yes
Checking for host processor xmm support...No
Checking that ptrace can change system call numbers...OK
Checking that host ptys support output SIGIO...Yes
Checking that host ptys support SIGIO on close...No, enabling workaround
Checking for /dev/anon on the host...Not available (open failed with 
errno 2)
NET: Registered protocol family 16
mconsole (version 2) initialized on 
/var/uml/machines/lars000/control/lars000/mconsole
SGI XFS with ACLs, no debug enabled
Initializing Cryptographic API
RAMDISK driver initialized: 16 RAM disks of 8192K size 1024 blocksize
NET: Registered protocol family 2
IP: routing cache hash table of 512 buckets, 4Kbytes
TCP: Hash tables configured (established 4096 bind 8192)
NET: Registered protocol family 1
NET: Registered protocol family 17
Initializing software serial port version 1
Kernel panic: read of switch_pipe failed, errno = 9
 <6>SysRq : Show Regs

EIP: 0023:[<a01c0682>] CPU: 0 Not tainted ESP: 002b:a3f386a4 EFLAGS: 
00200282
    Not tainted
EAX: 00000000 EBX: 00000001 ECX: a3f38744 EDX: a3f386c4
ESI: 00000008 EDI: 0000000a EBP: a3f386ac DS: 002b ES: 002b
Call Trace: [<a00378fb>] [<a001c44b>] [<a0044e8d>] [<a0036c4b>] 
[<a01d74f0>]
   [<a001d518>] [<a0204527>] [<a00394ab>] [<a00116a2>] [<a004805d>] 
[<a01c03d0>]
   [<a0047fd0>] [<a0016699>] [<a01c0754>] [<a0047fd0>] [<a001667e>] 
[<a0047fd0>]
   [<a001d750>] [<a0047fd0>] [<a01c0628>] [<a01c0682>]
sleeping process 10866 got unexpected signal : 11

-- Lars



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