vm_prefault: Warning, backing object race averted lobject

[YONETANI Tomokazu]

With heavier load using 6 jails, I could still trigger this same panic.
The kernel was built from source as of a5fc4.

On Mon, Sep 26, 2011 at 01:54:12PM +0900, YONETANI Tomokazu wrote:
> Hello.
> As I wrote in issue2118, after the fix (1f8fc82a) I started seeing
> warning messages on the console under load:
> 
>   vm_prefault: Warning, backing object race averted lobject 0xffffffe0749d3210
> 
> The system used to panic(backtrace at the end of this message) within
> a day or two, but with the kernel built from more recent source(fa7cb8ce),
> it no longer panics (well, at least for 4 days) running the same load
> (pkgsrc bulk build with MAKE_JOBS=5 defined), just the warning messages
> shown above all over the console.
> 
>     #4  0xffffffff8039c50f in panic (
> 	fmt=0xffffffff805edf90 "Bad link elm %p prev->next != elm")
> 	at /usr/src/sys/kern/kern_shutdown.c:833
>     #5  0xffffffff80532b35 in vm_object_deallocate_locked (
> 	object=0xffffffe0690b2d10) at /usr/src/sys/vm/vm_object.c:601
>     #6  0xffffffff80532c0f in vm_object_deallocate (object=0xffffffe06b9eed10)
> 	at /usr/src/sys/vm/vm_object.c:451
>     #7  0xffffffff8052d5bd in vm_map_entry_delete (countp=<optimized out>,
> 	entry=<optimized out>, map=<optimized out>)
> 	at /usr/src/sys/vm/vm_map.c:2608
>     #8  vm_map_delete (map=0xffffffe05b0d9a00, start=<optimized out>,
> 	end=140737488355328, countp=<optimized out>)
> 	at /usr/src/sys/vm/vm_map.c:2753
>     #9  0xffffffff8052d661 in vm_map_remove (map=0xffffffe05b0d9a00, start=0,
> 	end=<unavailable>) at /usr/src/sys/vm/vm_map.c:2774
>     #10 0xffffffff8052d6e9 in vmspace_terminate (vm=0xffffffe05b0d9a00)
> 	at /usr/src/sys/vm/vm_map.c:310
>     #11 0xffffffff80370579 in _sysref_put (sr=0xffffffe05b0d9bd0)
> 	at /usr/src/sys/kern/kern_sysref.c:325
>     #12 0xffffffff80388079 in sysref_put (sr=<optimized out>)
> 	at /usr/src/sys/sys/sysref2.h:83
>     #13 exit1 (rv=<optimized out>) at /usr/src/sys/kern/kern_exit.c:417
>     #14 0xffffffff803884a4 in sys_exit (uap=<optimized out>)
> 	at /usr/src/sys/kern/kern_exit.c:121
>     #15 0xffffffff805b0308 in syscall2 (frame=0xffffffe076d33c08)
> 	at /usr/src/sys/platform/pc64/x86_64/trap.c:1188
>     #16 0xffffffff805a88df in Xfast_syscall ()
> 	at /usr/src/sys/platform/pc64/x86_64/exception.S:320
>     #17 0x000000000000002b in ?? ()
> 
> 
> Best Regards,
> YONETANI Tomokazu