Thread join behaviour

[Alex Rønne Petersen]

On 14-04-2012 18:04, Russel Winder wrote:
> I thought the following would terminate gracefully having printed 0..9
> in some (random) order:
>
>          #! /usr/bin/env rdmd
>
>          import std.algorithm ;
>          import std.range ;
>          import std.stdio ;
>          import core.thread ;
>
>          int main ( immutable string[] args ) {
>            auto threads = map ! ( ( int a ) {
>                void delegate ( ) f ( ) {
>                  return delegate ( ) { writeln ( a ) ; } ;
>                }
>                return new Thread ( f )  ;
>              } ) ( iota ( 10 ) ) ;
>            foreach ( t ; threads ) { t.start ( ) ; }
>            foreach ( t ; threads ) { t.join ( ) ; }
>            return 0 ;
>          }
>
> However, this does not happen, at least with 2.059 on Linux as per
> Debian Unstable.  Instead I get:
>
>          1
>          2
>          4
>          5
>          8
>          3
>          7
>          6
>          9
>          0
>          core.thread.ThreadException at src/core/thread.d(906): Unable to join thread
>          ----------------
>          /tmp/.rdmd-1000/home/users/russel/Progs/OddsByLanguage/D/Odds/initializingWithAMap.d.9532BBED12C814F25F173A9AEAB96D0D(_Dmain+0x83) [0x425edb]
>          /tmp/.rdmd-1000/home/users/russel/Progs/OddsByLanguage/D/Odds/initializingWithAMap.d.9532BBED12C814F25F173A9AEAB96D0D(extern (C) int rt.dmain2..main(int, char**).void runMain()+0x17) [0x429bab]
>          /tmp/.rdmd-1000/home/users/russel/Progs/OddsByLanguage/D/Odds/initializingWithAMap.d.9532BBED12C814F25F173A9AEAB96D0D(extern (C) int rt.dmain2..main(int, char**).void tryExec(scope void delegate())+0x23) [0x42952b]
>          /tmp/.rdmd-1000/home/users/russel/Progs/OddsByLanguage/D/Odds/initializingWithAMap.d.9532BBED12C814F25F173A9AEAB96D0D(extern (C) int rt.dmain2..main(int, char**).void runAll()+0x3d) [0x429bf9]
>          /tmp/.rdmd-1000/home/users/russel/Progs/OddsByLanguage/D/Odds/initializingWithAMap.d.9532BBED12C814F25F173A9AEAB96D0D(extern (C) int rt.dmain2..main(int, char**).void tryExec(scope void delegate())+0x23) [0x42952b]
>          /tmp/.rdmd-1000/home/users/russel/Progs/OddsByLanguage/D/Odds/initializingWithAMap.d.9532BBED12C814F25F173A9AEAB96D0D(main+0xd3) [0x4294c3]
>          /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xfd) [0x7f1ed17f8ead]
>          ----------------
>
> I think I must be having a dumb moment as my reaction continues to be
> WTF.
>

http://www.kernel.org/doc/man-pages/online/pages/man3/pthread_join.3.html#ERRORS

We can rule out these:

EDEADLK: Can't happen with your code.
EINVAL (second case): No other thread is trying to join.
ESRCH: Shouldn't happen since druntime registers threads with libpthread.

So, the first case of EINVAL (thread is not a joinable thread) must be 
the cause. I have no clue *why* though...

-- 
- Alex