thread::create create 2 system threads instead of one

[Олег Н.]

Hi, all.

Can anybody explain why first call of thread::create makes 2 system threads instead of one?

For example, we have t.tcl script:
~$ cat t.tcl
#!/usr/bin/tclsh

package require Thread

puts "stage1"
after 10000
thread::create {thread::wait}

puts "stage2"
after 10000

thread::create {thread::wait}

puts "stage3"
after 10000

We run it. And check system threads on every stage change:
~$ ps -aL | grep t.tcl
8134 8134 pts/2 00:00:00 t.tcl
~$ ps -aL | grep t.tcl
8134 8134 pts/2 00:00:00 t.tcl
8134 8372 pts/2 00:00:00 t.tcl
8134 8373 pts/2 00:00:00 t.tcl
~$ ps -aL | grep t.tcl
8134 8134 pts/2 00:00:00 t.tcl
8134 8372 pts/2 00:00:00 t.tcl
8134 8373 pts/2 00:00:00 t.tcl
8134 8605 pts/2 00:00:00 t.tcl

[Harald Oehlmann]

Hi Oleg,
what is your platform? If it is linux, which threadding system was
compiled in (pthreads) (found by the configure script).

Take care,
Harald

[Олег Н.]

> Hi Oleg,
> what is your platform? If it is linux, which threadding system was
> compiled in (pthreads) (found by the configure script).

Oops. Forgot to say. I use Linux based os.
% array get tcl_platform
osVersion 5.4.247-my pointerSize 8 byteOrder littleEndian threaded 1 machine x86_64 platform unix pathSeparator : os Linux engine Tcl user lego wordSize 8
~$ ldd `which tclsh` | grep thread
libpthread.so.0 => /lib/libpthread.so.0 (0x00007f7bad070000)