Date: Mon, 14 Aug 2000 07:32:21 -0500 (CDT) From: Doug Lee <dgl@visi.com> To: freebsd-stable@freebsd.org Subject: pty race condition in 4.1? Message-ID: <Pine.BSF.4.21.0008140707060.10822-100000@kirk.dsl.visi.com>
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I was compiling a kernel under 4.1-20000806-STABLE inside of `script'
inside of `screen' when the `make depend' process blocked
unexpectedly: status I+, wchan "ttywri" (from `ps -axl'). The parent
`script' process stopped similarly: status I+, wchan "ptcin." I traced
"ptcin" to tty_pty.c in /usr/src/sys/kern--a tsleep call with that
label--unless I missed another reference ("traced" here means `grep', not
gdb/backtrace, which I didn't think of in time). I couldn't find a way to
unwedge the process without killing something, so I finally typed ^C in
the screen window running script/make, and script exited and left the make
process running with no place to send output. The wedge happened in the
middle of a HUGE (14,400 or so-character) line from `make depend' listing
C files; the cursor parked itself just after
"../../miscfs/procfs/procfs_regs.c," which is about 6,144 characters into
the line. I subsequently killed off the whole kernel build, did a `make
clean' in the compile subdirectory for my particular kernel, and started
over at `config.' The process ran fine this time.
I realize this is a complicated issue, what with script and screen and
make and its descendants all running at once; but I'm wondering if anyone
has seen anything like this. I can sure provide further system
information if requested, but I'm not sure what more would be helpful, nor
do I know of a way to predictably reproduce the problem. I was running
the generic kernel that came with the snapshot when this
happened. `script' is as it came with the snapshot; `screen' is out of
ports with no local tweaks unless my /etc/make.conf having
"CFLAGS=-pipe" in it affects that particular port's build process.
--
Doug Lee
dgl@visi.com
http://www.visi.com/~dgl
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