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

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

The following reply was made to PR kern/50375; it has been noted by GNATS.

From: Jeff Rizzo <riz%tastylime.net@localhost>
To: gnats-bugs%NetBSD.org@localhost, netbsd-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/50375: layerfs (nullfs) locking problem leading to livelock
Date: Thu, 29 Oct 2015 07:02:25 -0700

 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)