port-alpha/55652: bytes_transfer_eof_piod_write_i test causes kernel freeze

[rokuyama.rk%gmail.com@localhost]

>Number:         55652
>Category:       port-alpha
>Synopsis:       bytes_transfer_eof_piod_write_i test causes kernel freeze
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-alpha-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Sep 10 09:55:00 +0000 2020
>Originator:     Rin Okuyama
>Release:        9.99.72
>Organization:
Department of Physics, Meiji University
>Environment:
NetBSD ds10 9.99.72 NetBSD 9.99.72 (GENERIC-$Revision: 1.407 $) #3: Thu Sep 10 18:11:06 JST 2020  rin@latipes:/sys/arch/alpha/compile/DS10 alpha
>Description:
bytes_transfer_eof_piod_write_i test in tests/lib/libc/sys/t_ptrace_wait
causes kernel freeze on my DS10 (single-core 21264A processor), in which
no operation is possible except for entering DDB from console:

----
ds10# cd /usr/tests/lib/libc/sys
ds10# atf-run t_ptrace_wait
...
tc-end: 1599729844.489525, bytes_transfer_eof_piod_write_d, passed
tc-start: 1599729844.490780, bytes_transfer_eof_piod_write_i
----

Here's backtrace etc. obtained by DDB:

----
tc-start: 1599729844.490780, bytes_transfer_eof_piod_write_i
~Stopped in pid 637.637 (t_ptrace_wait) at       netbsd:cpu_Debugger+0x4:
ret     zero,(ra)
db> bt
cpu_Debugger() at netbsd:cpu_Debugger+0x4
comintr() at netbsd:comintr+0xb84
alpha_shared_intr_dispatch() at netbsd:alpha_shared_intr_dispatch+0x5c
sio_iointr() at netbsd:sio_iointr+0x44
interrupt() at netbsd:interrupt+0x214
XentInt() at netbsd:XentInt+0x1c
--- interrupt (from ipl 0) ---
rw_enter() at netbsd:rw_enter+0x1a0
vm_map_lock_read() at netbsd:vm_map_lock_read+0x20
uvm_fault_internal() at netbsd:uvm_fault_internal+0x10c
trap() at netbsd:trap+0x604
XentMM() at netbsd:XentMM+0x20
--- memory management fault ---
kcopyerr() at netbsd:kcopyerr+0xc
kcopy() at netbsd:kcopy+0x44
copyout_vmspace() at netbsd:copyout_vmspace+0x94
uiomove() at netbsd:uiomove+0xb8
uvm_io() at netbsd:uvm_io+0x140
process_domem() at netbsd:process_domem+0xa8
ptrace_doio() at netbsd:ptrace_doio+0x144
do_ptrace() at netbsd:do_ptrace+0xce4
sys_ptrace() at netbsd:sys_ptrace+0x3c
syscall() at netbsd:syscall+0x300
XentSys() at netbsd:XentSys+0x60
--- syscall (26) ---
--- user mode ---
db> ps
PID    LID S CPU     FLAGS       STRUCT LWP *               NAME WAIT
2108  2108 4   0   1000000   fffffc003f51ae80      t_ptrace_wait
637  > 637 7   0         0   fffffc003f51a600      t_ptrace_wait
184    184 3   0        80   fffffc003f51b2c0            atf-run poll
...
db> trace/a fffffc003f51a600
trace: pid 637 lid 637 at 0xfffffc000046dde8
mi_switch() at netbsd:mi_switch+0x228
db>
----

Full console log including dmesg is provided here:
	http://www.netbsd.org/~rin/alpha_log_20200910.txt

This should be a regression introduced after 2020-05-20, when I carried
out ATF and that test successfully passed.
>How-To-Repeat:
cd /usr/tests/lib/libc/sys && atf-run t_ptrace_wait
>Fix:
N/A