FreeBSD lock order reversal (LOR) #60

Then I looked into dmesg and found this LOR:
lock order reversal
 1st 0xc07bdd80 sched lock (sched lock) @ sys/kern/sys_process.c:657
 2nd 0xc07c1ac4 sleepq chain (sleepq chain) @ sys/kern/subr_sleepqueue.c:219
		
KDB: stack backtrace:
kdb_backtrace(c075c7bd,c07c1ac4,c075b8d7,c075b8d7,c075b8e4) at kdb_backtrace+0x2e
witness_checkorder(c07c1ac4,9,c075b8e4,db,c15964b4) at witness_checkorder+0x6aa
_mtx_lock_spin_flags(c07c1ac4,0,c075b8e4,db,d1a22b74) at _mtx_lock_spin_flags+0x8d
sleepq_lock(c15964b4,c1da57f0,c1da5858,c1955060,d1a22b98) at sleepq_lock+0x39
wakeup(c15964b4,1,c0756e2e,5ad,c1e60000) at wakeup+0x12
thread_continued(c1da57f0,0,c075d149,291,a) at thread_continued+0x9c
kern_ptrace(c1e37190,7,8cc,1,0) at kern_ptrace+0xadf
ptrace(c1e37190,d1a22d14,10,3ff,4) at ptrace+0xf0
syscall(2f,2f,2f,0,1871d) at syscall+0x270
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (26, FreeBSD ELF32, ptrace), eip = 0x28346fff, esp = 0xbfbfdf2c, ebp = 0xbfbfdfe8 ---
		

• freebsd-current (thread)
• commit (which SVN r#?)