Re: kern/55237

[Yorick Hardy <yorickhardy%gmail.com@localhost>]

The following reply was made to PR kern/55237; it has been noted by GNATS.

From: Yorick Hardy <yorickhardy%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/55237
Date: Fri, 22 May 2020 21:52:51 +0200

 Hi,
 
 I tried to narrow down the cause, by showing the v_usecount (u) and v_writecount (w)
 when the panic happens:
 
  https://nxr.netbsd.org/xref/src/sys/kern/vfs_vnode.c#788
 
 and it seems v_writecount is not zero when it was expected to be (it was 1). I am sorry,
 I have not made any further progress in tracking down the problem.
 
  Crash version 9.99.63, image version 9.99.63.
  crash: _kvm_kvatop(0)
  Kernel compiled without options LOCKDEBUG.
  System panicked: vrelel: bad ref count [u:1 w:1]
  Backtrace from time of crash is available.
  crash> bt
  _KERNEL_OPT_NAGR() at 0
  ?() at 7f7ff7ecf000
  sys_reboot() at sys_reboot
  vpanic() at vpanic+0x15b
  vtryrele() at vtryrele
  vcache_dealloc() at vcache_dealloc
  uvm_unmap_detach() at uvm_unmap_detach+0x63
  uvm_unmap1() at uvm_unmap1+0x4e
  uvm_mremap() at uvm_mremap+0x35a
  sys_mremap() at sys_mremap+0x68
  syscall() at syscall+0x1fd
  --- syscall (number 411) ---
  syscall+0x1fd:
 
 -- 
 Kind regards,
 
 Yorick Hardy