Re: [uml-devel] ubd_kern.c: spin_lock already locked by drivers/block/ll_rw_blk.c

Re: [uml-devel] ubd_kern.c: spin_lock already locked by drivers/block/ll_rw_blk.c

[Paolo Giarrusso]

Alle 11:19, mercoledì 11 giugno 2003, Carlo Wood ha scritto:
> Running 2.5.69 as uml, I get the following during boot:
>
> ...
> NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
>  /dev/ubd/disc0:arch/um/drivers/ubd_kern.c:383:
> spin_lock(arch/um/drivers/ubd_kern.c:a01b6940) already locked by
> drivers/block/ll_rw_blk.c/1002 drivers/block/ll_rw_blk.c:1004:
> spin_unlock(arch/um/drivers/ubd_kern.c:a01b6940) not locked unknown
> partition table
>  /dev/ubd/disc1:arch/um/drivers/ubd_kern.c:383:
> spin_lock(arch/um/drivers/ubd_kern.c:a01b6940) already locked by
> drivers/block/ll_rw_blk.c/1002 drivers/block/ll_rw_blk.c:1004:
> spin_unlock(arch/um/drivers/ubd_kern.c:a01b6940) not locked unknown
> partition table
> arch/um/drivers/ubd_kern.c:383:
> spin_lock(arch/um/drivers/ubd_kern.c:a01b6940) already locked by
> drivers/block/ll_rw_blk.c/1002 drivers/block/ll_rw_blk.c:1004:
> spin_unlock(arch/um/drivers/ubd_kern.c:a01b6940) not locked
> arch/um/drivers/ubd_kern.c:383:
> spin_lock(arch/um/drivers/ubd_kern.c:a01b6940) already locked by
> drivers/block/ll_rw_blk.c/1002 drivers/block/ll_rw_blk.c:1004:
> spin_unlock(arch/um/drivers/ubd_kern.c:a01b6940) not locked
> arch/um/drivers/ubd_kern.c:383:
> spin_lock(arch/um/drivers/ubd_kern.c:a01b6940) already locked by
> drivers/block/ll_rw_blk.c/1002 drivers/block/ll_rw_blk.c:1004:
> spin_unlock(arch/um/drivers/ubd_kern.c:a01b6940) not locked VFS: Mounted
> root (ext2 filesystem) readonly.
> ...
>
> This is with kernel debugging on, of course.
>
> Because it mentions files in arch/um/*, it must be a problem
> with the uml.
In fact, yes, it's a UML problem. I'm going to solve this. No, I'm not crazy, 
the problem is still here (the line numbers are different, but probably is 
the same). As a side note, to get this you need CONFIG_SMP=n and 
CONFIG_DEBUG_SPINLOCK=y. If you enable CONFIG_SMP, you actually don't get the 
debug messages, only the deadlock. Also, to get *this* messages you need to 
be using synchronous mode. I recommend *NOT* enabling 
CONFIG_BLK_DEV_UBD_SYNC, but using instead the ubd=sync option (which is the 
same thing, but selectable at runtime).

**And no, using the 's' ubd0s=... is not the same thing; the second just means 
"use O_SYNC", while the first means "always use O_SYNC, and also don't start 
the ubd I/O thread".
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729



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