LOR with page queue mutex and vm object

[Alan L. Cox]

Kris Kennaway wrote:
> 
> I got this on alpha just now (kernel updated 2 days ago, filesystems
> created with -b 32768 -f 4096 to test reports of panics with these
> settings, which may or may not be relevant).  I don't think I've seen
> this trace before...apologies if it's another false positive.
> 

This is real.  I'll look into it.

Thanks,
Alan

> 
>  1st 0xfffffc00006e48d0 vm page queue mutex (vm page queue mutex) @ /a/asami/portbuild/alpha/src-client/sys/vm/vm_pageout.c:405
>  2nd 0xfffffc0005102e00 vm object (vm object) @ /a/asami/portbuild/alpha/src-client/sys/kern/vfs_bio.c:2280
> Stack backtrace:
> db_print_backtrace() at db_print_backtrace+0x18
> backtrace() at backtrace+0x2c
> witness_lock() at witness_lock+0x6fc
> _mtx_lock_flags() at _mtx_lock_flags+0xc8
> vfs_setdirty() at vfs_setdirty+0x7c
> bdwrite() at bdwrite+0x3b8
> ffs_update() at ffs_update+0x388
> ufs_inactive() at ufs_inactive+0x254
> ufs_vnoperate() at ufs_vnoperate+0x2c
> vput() at vput+0x170
> vm_pageout_scan() at vm_pageout_scan+0x7ac
> vm_pageout() at vm_pageout+0x3ac
> fork_exit() at fork_exit+0x100
> exception_return() at exception_return
> -
> 
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>    Part 1.2Type: application/pgp-signature