[Xen-bugs] [Bug 1535] New: panic: iret exception

[bugzilla-daemon@xxxxxxxxxxxxxxxxxxx]

http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1535

           Summary: panic: iret exception
           Product: Xen
           Version: unstable
          Platform: x86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Unspecified
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: micah@xxxxxxxxxx


I'm getting a regular kernel oops, causing my dom0 to crash (either freeze or
reboot). I captured the oops and it clearly looks like a xen bug. The kernel
does some I/O, which gets queued, but for some reason the request causes a
violation in xen.

I found other debian folks were also having this same crash, theirs were also
similarly related to irq or scheduling issues, all resulting in iret
exceptions. You can see their reported bugs over at:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504805


First the crash                                               

 [ 6930.059040] iret exception: 0000 [#1] SMP 
 [ 6930.059123] Modules linked in: xt_tcpudp xt_physdev iptable_filter
ip_tables x_tables netloop tun bridge ipv6 loop evdev container button i2c_i801
i2c
 [ 6930.060105]
 [ 6930.060146] Pid: 1241, comm: md1_resync Not tainted  (2.6.26-1-xen-686 #1)
 [ 6930.060196] EIP: 0061:[<c01011a7>] EFLAGS: 00000002 CPU: 0
 [ 6930.060246] EIP is at 0xc01011a7
 [ 6930.060283] EAX: 00000000 EBX: ecfa3df0 ECX: 00000001 EDX: 00000001
 [ 6930.060331] ESI: ecfa3df0 EDI: c1118e20 EBP: ece26040 ESP: ecfa3db4
 [ 6930.060378] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0069
 [ 6930.060420] Process md1_resync (pid: 1241, ti=ecfa2000 task=ece26040
task.ti=ec806000)
 [ 6930.060472] Stack: c0102eb7 c1118e20 ece26040 ece2628c c111906c 00000000
00000001 ed4cac84
 [ 6930.060501] ecd98ef0 ed4cac80 ebc08cac 00000003 c01db664 ebc08cac ecfa3e10
00000003
 [ 6930.060501] 00000000 00000068 ecfa3ff8 db744000 00000002 ecfa8f00 c10c2038
00001000
 [ 6930.060501] Call Trace:
 [ 6930.060501] [<c0102eb7>] __switch_to+0x376/0x42e
 [ 6930.060501] [<c01db664>] cfq_add_rq_rb+0x5c/0x6b
 [ 6930.060501] [<c01cf34e>] elv_merged_request+0x28/0x30
 [ 6930.060501] [<c01d2140>] __make_request+0x294/0x36e
 [ 6930.060502] [<c01d0eb1>] generic_make_request+0x34d/0x37b
 [ 6930.060502] [<c0105f7c>] get_nsec_offset+0xe/0x6a
 [ 6930.060573] [<c0106151>] get_runstate_snapshot+0x69/0xec
 [ 6930.060573] [<c0115353>] update_curr+0x47/0x79
 [ 6930.060573] [<c01160a3>] dequeue_entity+0x13/0x9b
 [ 6930.060573] [<c0115fa3>] __dequeue_entity+0x1f/0x71
 [ 6930.060573] [<c02ca3a2>] schedule+0x616/0x6b1
 [ 6930.060573] [<c0105b0d>] do_IRQ+0x52/0x65
 [ 6930.060573] [<c02ca5dd>] schedule_timeout+0x13/0x86
 [ 6930.060573] [<c012ed33>] prepare_to_wait+0x12/0x49
 [ 6930.060573] [<ee1a6411>] md_thread+0x9c/0xcd [md_mod]
 [ 6930.060573] [<c012ec28>] autoremove_wake_function+0x0/0x2d
 [ 6930.060573] [<ee1a6375>] md_thread+0x0/0xcd [md_mod]
 [ 6930.060573] [<c012eb65>] kthread+0x38/0x5f
 [ 6930.060573] [<c012eb2d>] kthread+0x0/0x5f
 [ 6930.060573] [<c0104267>] kernel_thread_helper+0x7/0x10
 [ 6930.060573] =======================
 [ 6930.060573] Code: cc cc cc cc b8 0c 00 00 00 cd 82 c3 cc cc cc cc
 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc b8 0d 00
 00 00 cd 82 <c3

 [ 6930.060573] EIP: [<c01011a7>] 0xc01011a7 SS:ESP 0069:ecfa3db4

 Then, I fed each of the [<xxxx>] numbers through addr2line, including
 the EIP, which gives us:

 lenny:~/kernel/linux-2.6-2.6.26# addr2line -e
./debian/build/build_i386_xen_686/vmlinux

 c0102eb7

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/include/xen/hypercall.h:13

 c01db664

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/block/cfq-iosched.c:1464

 c01cf34e

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/block/elevator.c:118

 c01d2140

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/block/blk-core.c:413

 c01d0eb1

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/block/blk-core.c:1228

 c0105f7c

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/arch/x86/kernel/time_32-xen.c:235

 c0106151

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/arch/x86/kernel/time_32-xen.c:206

 c0115353

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/kernel/sched_fair.c:433

 c01160a3

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/kernel/sched_fair.c:738

 c0105b0d

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/include/asm/irq_regs_32.h:24

 c02ca5dd

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/kernel/sched_stats.h:195

 c012ed33

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/kernel/wait.c:125

 ee1a6411
 ??:0

 c012ec28

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/kernel/wait.c:248

 ee1a6375
 ??:0

 c012eb65

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/kernel/kthread.c:150

 c012eb2d

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/include/linux/list.h:45

 c0104267

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/arch/x86/kernel/entry_32-xen.S:1259

 c01011a7

/root/kernel/linux-2.6-2.6.26/debian/build/build_i386_xen_686/arch/x86/kernel/head_32-xen.S:72


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