Bug 28466

I have instrumentation in the syscall path to catch cases where the 
cpl after the syscall is not 0. I also have soft updates enabled.

When I type reboot at which time a some daemons in my system are doing
a bunch of fsyncs, I get the following error from my instrumentation.

Syscall 95 entered at cpl 0, exited at cpl 3fc0000

(kgdb) bt
#0  dumpsys () at ../../kern/kern_shutdown.c:562
#1  0xc018fbab in boot (howto=256) at ../../kern/kern_shutdown.c:317
#2  0xc01903e6 in panic (
    fmt=0xc0379be0 "Syscall %d entered at cpl %x, exited at cpl %x\n")
    at ../../kern/kern_shutdown.c:807
#3  0xc032192f in syscall2 (frame={tf_fs = 47, tf_es = 47, tf_ds = 47, 
      tf_edi = 528384, tf_esi = 0, tf_ebp = -1077938608, tf_isp = -577204268, 
      tf_ebx = 7, tf_edx = 1209838208, tf_ecx = 1610641556, tf_eax = 0, 
      tf_trapno = 12, tf_err = 2, tf_eip = 1209555732, tf_cs = 31, 
      tf_eflags = 642, tf_esp = -1077949932, tf_ss = 47})
    at ../../i386/i386/trap.c:1450
#4  0xc0314685 in Xint0x80_syscall () at ../../i386/i386/elf_machdep.c:120
(kgdb) p lk
$1 = {lkt_spl = 66846720, lkt_held = -1}


I do not have any problems when soft updates is not enabled. I guess 
there is some code in the fsync path that is not doing an splx.

I added the fix for 'Free lock before returning from
process_worklist_item' (1.88 ffs_softdep.c), but that did not help.

How-To-Repeat: 1) Add instrumentation in trap.c to panic if the cpl after a syscall 
is not zero.
2) Enable softupdates
3) Touch a lot of files
4) Do fsyncs

Again, I do not hit this all the time. I have seen it twice in 20
attempts.
reboot