Original bug ID: 1453
Reporter: administrator
Status: closed
Resolution: fixed
Priority: normal
Severity: minor
Category: ~DO NOT USE (was: OCaml general)

Bug description

Full_Name: Sven Luther
Version: 3.06
OS: Debian GNU/Linux
Submission from: astrasbourg-206-1-18-22.abo.wanadoo.fr (81.49.129.22)

Hello,

la@iki.fi submitted me this bug report :

===============BEGIN===============
Problem: take any program, such as:

(* t.ml *)

let rec thr str =
print_string str;
print_newline ();
Thread.delay 1.0;
thr str

let _ =
ignore (Thread.create thr "foo");
ignore (Thread.create thr "bar");
read_line ()

...and native-compile it with thread support:

$ ocamlopt -o t -thread unix.cmxa threads.cmxa t.ml

It works, all right:

$ ./t
foo
bar
foo
bar
foo
bar

...and creates two extra threads, one is ocaml's tick thread, the other,
dunno, something used internally by linuxthreads?

$ ps -C t
PID TTY TIME CMD
12240 pts/5 00:00:00 t
12241 pts/5 00:00:00 t
12242 pts/5 00:00:00 t
12243 pts/5 00:00:00 t
12244 pts/5 00:00:00 t

Now control-C the program, and it stops. But:

$ ps -C t
PID TTY TIME CMD
12242 pts/5 00:00:00 t

And this is apparently the "tick" thread:

$ strace -p 12242
select(0, NULL, NULL, NULL, {0, 10000}) = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 50000}) = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 50000}) = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 50000}) = 0 (Timeout)

It has to be killed with kill -9. Not fun.
===============END=======================

I confirmed this, but it doesn't happen all the time, maybe 1/2 or 1/3 of the
time.

Maybe it is related to the moment the threaded program is interrupted.

Friendly,

Sven Luther