Re: kern/50375: layerfs (nullfs) locking problem leading to livelock

[Jeff Rizzo <riz%tastylime.net@localhost>]

Gladly:

(gdb) kvm proc 0x95768060
0x812e9eb8 in mi_switch (l=l@entry=0x95768060) at 
/home/riz/src/sys/kern/kern_synch.c:719
719    in /home/riz/src/sys/kern/kern_synch.c
(gdb) fr 9
#9  0x81355670 in lookup_once (state=state@entry=0xa3bc5d28, 
searchdir=0x948159a0, newsearchdir_ret=newsearchdir_ret@entry=0xa3bc5cb4,
    foundobj_ret=foundobj_ret@entry=0xa3bc5cb8) at 
/home/riz/src/sys/kern/vfs_lookup.c:1067
1067    /home/riz/src/sys/kern/vfs_lookup.c: No such file or directory.
(gdb)  print foundobj
$1 = (struct vnode *) 0x9246d850
(gdb)  print *foundobj
$2 = {v_uobj = {vmobjlock = 0x91f3f640, pgops = 0x81423cc0 
<uvm_vnodeops>, memq = {tqh_first = 0x0, tqh_last = 0x9246d858}, 
uo_npages = 0, uo_refs = 1, rb_tree = {
      rbt_root = 0x0, rbt_ops = 0x81423c00 <uvm_page_tree_ops>, 
rbt_minmax = {0x0, 0x0}}, uo_ubc = {lh_first = 0x0}}, v_cv = {cv_opaque 
= {0x0, 0x9246d87c, 0x8146e51c}},
  v_size = 0, v_writesize = 0, v_iflag = 0, v_vflag = 16, v_uflag = 0, 
v_numoutput = 0, v_writecount = 0, v_holdcnt = 0, v_synclist_slot = 0, 
v_mount = 0x94c60008,
  v_op = 0x9159ac48, v_freelist = {tqe_next = 0x0, tqe_prev = 
0x9436ef8c}, v_freelisthd = 0x0, v_mntvnodes = {tqe_next = 0x0, tqe_prev 
= 0x94815a18}, v_cleanblkhd = {
    lh_first = 0x0}, v_dirtyblkhd = {lh_first = 0x0}, v_synclist = 
{tqe_next = 0x0, tqe_prev = 0x0}, v_dnclist = {lh_first = 0x0}, v_nclist 
= {lh_first = 0x0}, v_un = {
    vu_mountedhere = 0x0, vu_socket = 0x0, vu_specnode = 0x0, 
vu_fifoinfo = 0x0, vu_ractx = 0x0}, v_type = VDIR, v_tag = VT_NULL, 
v_lock = {rw_owner = 0}, v_data = 0x966580b0,
  v_klist = {slh_first = 0x0}}
(gdb)