Re: LOR kqueue / sleep mtxpool for LOR list

On Tue, Dec 18, 2007 at 10:20:21AM -1000, Jeff Roberson wrote:

On Tue, 18 Dec 2007, Ed Maste wrote:

I just saw this LOR during startup of an application while testing
8-CURRENT on a dev box. I've done no investigation yet.

FreeBSD TPC-D13-08.phaedrus 8.0-CURRENT FreeBSD 8.0-CURRENT #0: Mon Dec 17
16:27:54 EST 2007
emaste@xxxxxxxxxxxxxxxxxxx:/d2/emaste/HEAD/obj/d2/emaste/HEAD/src/sys/GENERIC i386

lock order reversal:
1st 0xc42b7580 kqueue (kqueue) @
/d2/emaste/HEAD/src/sys/kern/kern_event.c:1397
2nd 0xc3ece8e0 sleep mtxpool (sleep mtxpool) @
/d2/emaste/HEAD/src/sys/kern/sys_generic.c:1255
[...]

Thanks, this is interesting. The mtxpool should always be the leaf. The
opposite order is the bug. Can you add them to the static order list and
tell me where the reverse order is observed?

After adding it to the list this is what I got:

Mounting NFS file systems:lock order reversal:
1st 0xc3ece280 sleep mtxpool (sleep mtxpool) @ /d2/emaste/HEAD/src/sys/kern/kern_event.c:993
2nd 0xc4320d80 kqueue (kqueue) @ /d2/emaste/HEAD/src/sys/kern/kern_event.c:1001
KDB: stack backtrace:
db_trace_self_wrapper(c0b08831,e683daac,c079cabe,c0b0ada3,c4320d80,...) at db_trace_self_wrapper+0x26
kdb_backtrace(c0b0ada3,c4320d80,c0b01d5d,c0b01d5d,c0b01a4d,...) at kdb_backtrace+0x29
witness_checkorder(c4320d80,9,c0b01a4d,3e9,7db,...) at witness_checkorder+0x6de
_mtx_lock_flags(c4320d80,0,c0b01a4d,3e9,0,...) at _mtx_lock_flags+0xbc
kqueue_acquire(c445eaa0,4,e683db5c,c0b04436,f0,...) at kqueue_acquire+0x72
kern_kevent(c445eaa0,4,1,1,e683dc60,...) at kern_kevent+0x47
kevent(c445eaa0,e683dcfc,18,c0b0bacf,c0bb92e8,...) at kevent+0x19b
syscall(e683dd38) at syscall+0x2b3
Xint0x80_syscall() at Xint0x80_syscall+0x20
--- syscall (363, FreeBSD ELF32, kevent), eip = 0x2813dafb, esp = 0xbfbfd28c, ebp = 0xbfbfd388 ---

-Ed
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