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kernel BUG at drivers/block/loop.c:621

DISCUSSION Rob Landley 2 participants 4 messages Mar 18, 2006 User-mode Linux (UML)

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Rob Landley

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#0 lore raw

I can reproduce the following in 2.6.16-rc5, User Mode Linux:

kernel BUG at drivers/block/loop.c:621!

Kernel panic - not syncing: BUG!

EIP: 0073:[<ffffe410>] CPU: 0 Not tainted ESP: 007b:b7de1f9c EFLAGS: 00200246
Not tainted
EAX: 00000000 EBX: 000018be ECX: 00000013 EDX: 000018be
ESI: 000018bb EDI: 00000011 EBP: b7de1fb8 DS: 007b ES: 007b

09b87bb4:  [<0806c762>] show_regs+0x102/0x110
09b87bd0:  [<0805b6fc>] panic_exit+0x2c/0x50
09b87be0:  [<0807ff7d>] notifier_call_chain+0x2d/0x50
09b87c00:  [<08071095>] panic+0x75/0x120
09b87c20:  [<0812e181>] loop_thread+0x151/0x160
09b87c4c:  [<08065297>] run_kernel_thread+0x37/0x60
09b87cfc:  [<0805bbd1>] new_thread_handler+0x91/0xc0
09b87d20:  [<ffffe420>] disks+0xf7e7ec84/0x4

The reproduction sequence is a bit involved (my mount regression test and the current svn snapshot of busybox are involved), and running the following sequence of commands:

mount; mount -a; mount; mount /dev/loop1 /images/vfat.dir ; losetup /dev/loop1; ls; vi /etc/fstab; cat /etc/fstab; losetup /dev/loop0; mount /images/vfat.img /images/vfat.dir -o ro

The current busybox mount is still broken in a couple of known places (hence the testing; I'm fixing it). But it probably shouldn't panic the kernel...

Rob

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#1 lore raw
Quoted 9 lines · Rob Landley

I can reproduce the following in 2.6.16-rc5, User Mode Linux:

kernel BUG at drivers/block/loop.c:621!

Kernel panic - not syncing: BUG!

EIP: 0073:[<ffffe410>] CPU: 0 Not tainted ESP: 007b:b7de1f9c EFLAGS:
00200246 Not tainted
EAX: 00000000 EBX: 000018be ECX: 00000013 EDX: 000018be
ESI: 000018bb EDI: 00000011 EBP: b7de1fb8 DS: 007b ES: 007b

Quoted 7 lines
09b87bb4:  [<0806c762>] show_regs+0x102/0x110
09b87bd0:  [<0805b6fc>] panic_exit+0x2c/0x50
09b87be0:  [<0807ff7d>] notifier_call_chain+0x2d/0x50
09b87c00:  [<08071095>] panic+0x75/0x120
09b87c20:  [<0812e181>] loop_thread+0x151/0x160
09b87c4c:  [<08065297>] run_kernel_thread+0x37/0x60
09b87cfc:  [<0805bbd1>] new_thread_handler+0x91/0xc0

The below is strange - GCC is putting disks in the .text section or kallsyms has some bug.

Quoted 6 lines

09b87d20: [<ffffe420>] disks+0xf7e7ec84/0x4

The reproduction sequence is a bit involved (my mount regression test and the current svn snapshot of busybox are involved), and running the following sequence of commands:

Quoted 7 lines

mount; mount -a; mount; mount /dev/loop1 /images/vfat.dir ; losetup /dev/loop1; ls; vi /etc/fstab; cat /etc/fstab; losetup /dev/loop0; mount /images/vfat.img /images/vfat.dir -o ro

The current busybox mount is still broken in a couple of known places (hence the testing; I'm fixing it). But it probably shouldn't panic the kernel...

*) Is this reproducible on host?

*) I don't understand yet what UML may be doing wrong.
*) look at: that spin_lock (SMP kernel? SPINLOCK_DEBUG? Try enabling the latter and see what happens).

(a bio is a block I/O request)
*) given what the code says, on that line bio is NULL, i.e. loop_get_bio returned NULL, i.e. (I guess) wait_for_completion_interruptible returned, because someone else (loop_make_request) did "complete" on its param, but incorrectly as the "someone else" hadn't filled the lo->lo_bio.

Signature · 8 lines
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Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

		
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author
#2 lore raw
Quoted 18 lines · Blaisorblade
Quoted 9 lines · Rob Landley

I can reproduce the following in 2.6.16-rc5, User Mode Linux:

kernel BUG at drivers/block/loop.c:621!

Kernel panic - not syncing: BUG!

EIP: 0073:[<ffffe410>] CPU: 0 Not tainted ESP: 007b:b7de1f9c EFLAGS:
00200246 Not tainted
EAX: 00000000 EBX: 000018be ECX: 00000013 EDX: 000018be
ESI: 000018bb EDI: 00000011 EBP: b7de1fb8 DS: 007b ES: 007b

Quoted 7 lines
09b87bb4:  [<0806c762>] show_regs+0x102/0x110
09b87bd0:  [<0805b6fc>] panic_exit+0x2c/0x50
09b87be0:  [<0807ff7d>] notifier_call_chain+0x2d/0x50
09b87c00:  [<08071095>] panic+0x75/0x120
09b87c20:  [<0812e181>] loop_thread+0x151/0x160
09b87c4c:  [<08065297>] run_kernel_thread+0x37/0x60
09b87cfc:  [<0805bbd1>] new_thread_handler+0x91/0xc0
Quoted 4 lines

The below is strange - GCC is putting disks in the .text section or kallsyms has some bug.

Quoted 1 line

09b87d20: [<ffffe420>] disks+0xf7e7ec84/0x4

Isn't ffffe??? the FASTCALL page?

Quoted 8 lines
Quoted 8 lines

The reproduction sequence is a bit involved (my mount regression test and the current svn snapshot of busybox are involved), and running the following sequence of commands:

mount; mount -a; mount; mount /dev/loop1 /images/vfat.dir ; losetup /dev/loop1; ls; vi /etc/fstab; cat /etc/fstab; losetup /dev/loop0; mount /images/vfat.img /images/vfat.dir -o ro

Quoted 5 lines
Quoted 3 lines

The current busybox mount is still broken in a couple of known places (hence the testing; I'm fixing it). But it probably shouldn't panic the kernel...

*) Is this reproducible on host?

Haven't tried. I value my laptop. :)

My host is running unbuntu 2.6.12, and my mount test requires a clean environment with nothing else mounted when it first runs. (It basically needs to run as PID 1. Among other things, it synthesizes variants of its own fstab...)

I don't think it's a uml bug, but I cc'd the UML list because that's where I can easily reproduce it.

Rob

Signature · 12 lines
Never bet against the cheap plastic solution.


-------------------------------------------------------
This SF.Net email is sponsored by xPML, a groundbreaking scripting language
that extends applications into web and mobile media. Attend the live webcast
and join the prime developer group breaking into this new coding territory!
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
_______________________________________________
User-mode-linux-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
#3 lore raw
Quoted 19 lines · Rob Landley
Quoted 18 lines · Blaisorblade
Quoted 16 lines · Rob Landley

I can reproduce the following in 2.6.16-rc5, User Mode Linux:

kernel BUG at drivers/block/loop.c:621!

Kernel panic - not syncing: BUG!

EIP: 0073:[<ffffe410>] CPU: 0 Not tainted ESP: 007b:b7de1f9c EFLAGS:
00200246 Not tainted
EAX: 00000000 EBX: 000018be ECX: 00000013 EDX: 000018be
ESI: 000018bb EDI: 00000011 EBP: b7de1fb8 DS: 007b ES: 007b

09b87bb4:  [<0806c762>] show_regs+0x102/0x110
09b87bd0:  [<0805b6fc>] panic_exit+0x2c/0x50
09b87be0:  [<0807ff7d>] notifier_call_chain+0x2d/0x50
09b87c00:  [<08071095>] panic+0x75/0x120
09b87c20:  [<0812e181>] loop_thread+0x151/0x160
09b87c4c:  [<08065297>] run_kernel_thread+0x37/0x60
09b87cfc:  [<0805bbd1>] new_thread_handler+0x9 1/0xc0
Quoted 6 lines
Quoted 4 lines

The below is strange - GCC is putting disks in the .text section or kallsyms has some bug.

Quoted 1 line

09b87d20: [<ffffe420>] disks+0xf7e7ec84/0x4

Isn't ffffe??? the FASTCALL page?

Sorry, didn't mention that according to ctags, disks is defined only as a struct member or as a static variable... clearly neither is valid on a call stack.

The call trace decoder filters out hex values outside _stext - _etext, but maybe it also considers valid the FASTCALL page... leading to this interesting bogus output :-)

Quoted 9 lines

Haven't tried. I value my laptop. :)

My host is running unbuntu 2.6.12, and my mount test requires a clean environment with nothing else mounted when it first runs. (It basically needs to run as PID 1. Among other things, it synthesizes variants of its own fstab...)

I don't think it's a uml bug, but I cc'd the UML list because that's where I can easily reproduce it.

Ok - didn't notice the LKML cc, sorry (it's really late).

Quoted 1 line

Rob

Signature · 8 lines
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

		
___________________________________ 
Yahoo! Messenger with Voice: chiama da PC a telefono a tariffe esclusive 
http://it.messenger.yahoo.com