`await`ing a Promise in a different thread sometimes hangs

[p6rt]

Migrated from rt.perl.org#122709 (status was 'resolved')

Searchable as RT122709$

[p6rt]

From @lizmat

(since leont has been so busy with other stuff, I thought to report the problem he found)

12​:11 * leont suspects he's observing Promise.allof spinlocking or some such. 100% CPU usage, but no input is coming in :-/
12​:19 lizmat leont​: could you gist that ?
12​:22 leont Would need to reduce it first, but sure
13​:14 leont My spinlock seems to have gone away when I await()ed in the same thread that created the Proc​::Async
13​:16 lizmat leont​: interesting datapoint :-)
13​:16 wonder what jnthn would want to say about that :-)
13​:22 leont perl6 -e 'my $waiter = Proc​::Async.new(​:path($*EXECUTABLE), :args(["helper.pl"])).start; await start { await $waiter };'
13​:23 Let's make that easier​: perl6 -e 'my $waiter = Proc​::Async.new(​:path("echo"), :args(<Hello World>)).start; await start { await $waiter };'
13​:29 moritz leont++ # golfing
13​:30 leont​: could you please submit that to rakudobugperl.org?
13​:30 leont Sure

[p6rt]

From @lizmat

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[p6rt]

From @coke

On Fri Sep 05 14​:44​:06 2014, elizabeth wrote​:

(since leont has been so busy with other stuff, I thought to report
the problem he found)

12​:11 * leont suspects he's observing Promise.allof spinlocking or
some such. 100% CPU usage, but no input is coming in :-/
12​:19 lizmat leont​: could you gist that ?
12​:22 leont Would need to reduce it first, but sure
13​:14 leont My spinlock seems to have gone away when I await()ed
in the same thread that created the Proc​::Async…
13​:16 lizmat leont​: interesting datapoint :-)
13​:16 wonder what jnthn would want to say about that :-)
13​:22 leont perl6 -e 'my $waiter =
Proc​::Async.new(​:path($*EXECUTABLE), :args(["helper.pl"])).start;
await start { await $waiter };'
13​:23 Let's make that easier​: perl6 -e 'my $waiter =
Proc​::Async.new(​:path("echo"), :args(<Hello World>)).start; await
start { await $waiter };'
13​:29 moritz leont++ # golfing
13​:30 leont​: could you please submit that to
rakudobugperl.org?
13​:30 leont Sure

This seems to work with no issue here. Is this ticket closable?

$ perl6 -e 'my $waiter = Proc​::Async.new(​:path("echo"), :args(<Hello World>)).start; await start { await $waiter };'
Hello World

--
Will "Coke" Coleda

[p6rt]

The RT System itself - Status changed from 'new' to 'open'

[p6rt]

From @LLFourn

Not sure if it's relevant here but last time I checked there is an issues
with await and Proc​::Async on Mac.

RT #​125758 for example which looks similar to this.
On Wed, 27 Apr 2016 at 7​:08 AM, Will Coleda via RT <
perl6-bugs-followup@​perl.org> wrote​:

On Fri Sep 05 14​:44​:06 2014, elizabeth wrote​:

(since leont has been so busy with other stuff, I thought to report
the problem he found)

12​:11 * leont suspects he's observing Promise.allof spinlocking or
some such. 100% CPU usage, but no input is coming in :-/
12​:19 lizmat leont​: could you gist that ?
12​:22 leont Would need to reduce it first, but sure
13​:14 leont My spinlock seems to have gone away when I await()ed
in the same thread that created the Proc​::Async…
13​:16 lizmat leont​: interesting datapoint :-)
13​:16 wonder what jnthn would want to say about that :-)
13​:22 leont perl6 -e 'my $waiter =
Proc​::Async.new(​:path($*EXECUTABLE), :args(["helper.pl"])).start;
await start { await $waiter };'
13​:23 Let's make that easier​: perl6 -e 'my $waiter =
Proc​::Async.new(​:path("echo"), :args(<Hello World>)).start; await
start { await $waiter };'
13​:29 moritz leont++ # golfing
13​:30 leont​: could you please submit that to
rakudobugperl.org?
13​:30 leont Sure

This seems to work with no issue here. Is this ticket closable?

$ perl6 -e 'my $waiter = Proc​::Async.new(​:path("echo"), :args(<Hello
World>)).start; await start { await $waiter };'
Hello World

--
Will "Coke" Coleda

[p6rt]

From @LLFourn

Now I'm at home I tried it on my Mac, I can confirm that​:

perl6 -e 'my $waiter = Proc​::Async.new(​:path<echo>, :args<Hello
World>).start; await start { await $waiter }'

prints Hello World and then hangs forever.

On Wed, Apr 27, 2016 at 2​:58 PM Lloyd Fournier <lloyd.fourn@​gmail.com>
wrote​:

Not sure if it's relevant here but last time I checked there is an issues
with await and Proc​::Async on Mac.

RT #​125758 for example which looks similar to this.
On Wed, 27 Apr 2016 at 7​:08 AM, Will Coleda via RT <
perl6-bugs-followup@​perl.org> wrote​:

On Fri Sep 05 14​:44​:06 2014, elizabeth wrote​:

(since leont has been so busy with other stuff, I thought to report
the problem he found)

12​:11 * leont suspects he's observing Promise.allof spinlocking or
some such. 100% CPU usage, but no input is coming in :-/
12​:19 lizmat leont​: could you gist that ?
12​:22 leont Would need to reduce it first, but sure
13​:14 leont My spinlock seems to have gone away when I await()ed
in the same thread that created the Proc​::Async…
13​:16 lizmat leont​: interesting datapoint :-)
13​:16 wonder what jnthn would want to say about that :-)
13​:22 leont perl6 -e 'my $waiter =
Proc​::Async.new(​:path($*EXECUTABLE), :args(["helper.pl"])).start;
await start { await $waiter };'
13​:23 Let's make that easier​: perl6 -e 'my $waiter =
Proc​::Async.new(​:path("echo"), :args(<Hello World>)).start; await
start { await $waiter };'
13​:29 moritz leont++ # golfing
13​:30 leont​: could you please submit that to
rakudobugperl.org?
13​:30 leont Sure

This seems to work with no issue here. Is this ticket closable?

$ perl6 -e 'my $waiter = Proc​::Async.new(​:path("echo"), :args(<Hello
World>)).start; await start { await $waiter };'
Hello World

--
Will "Coke" Coleda

[p6rt]

From @coke

On Wed Apr 27 03​:02​:14 2016, lloyd.fourn@​gmail.com wrote​:

Now I'm at home I tried it on my Mac, I can confirm that​:

perl6 -e 'my $waiter = Proc​::Async.new(​:path<echo>, :args<Hello
World>).start; await start { await $waiter }'

prints Hello World and then hangs forever.

On Wed, Apr 27, 2016 at 2​:58 PM Lloyd Fournier <lloyd.fourn@​gmail.com>
wrote​:

Not sure if it's relevant here but last time I checked there is an issues
with await and Proc​::Async on Mac.

RT #​125758 for example which looks similar to this.
On Wed, 27 Apr 2016 at 7​:08 AM, Will Coleda via RT <
perl6-bugs-followup@​perl.org> wrote​:

On Fri Sep 05 14​:44​:06 2014, elizabeth wrote​:

(since leont has been so busy with other stuff, I thought to report
the problem he found)

12​:11 * leont suspects he's observing Promise.allof spinlocking or
some such. 100% CPU usage, but no input is coming in :-/
12​:19 lizmat leont​: could you gist that ?
12​:22 leont Would need to reduce it first, but sure
13​:14 leont My spinlock seems to have gone away when I await()ed
in the same thread that created the Proc​::Async…
13​:16 lizmat leont​: interesting datapoint :-)
13​:16 wonder what jnthn would want to say about that :-)
13​:22 leont perl6 -e 'my $waiter =
Proc​::Async.new(​:path($*EXECUTABLE), :args(["helper.pl"])).start;
await start { await $waiter };'
13​:23 Let's make that easier​: perl6 -e 'my $waiter =
Proc​::Async.new(​:path("echo"), :args(<Hello World>)).start; await
start { await $waiter };'
13​:29 moritz leont++ # golfing
13​:30 leont​: could you please submit that to
rakudobugperl.org?
13​:30 leont Sure

This seems to work with no issue here. Is this ticket closable?

$ perl6 -e 'my $waiter = Proc​::Async.new(​:path("echo"), :args(<Hello
World>)).start; await start { await $waiter };'
Hello World

--
Will "Coke" Coleda

Can you include the output of sw_vers and perl6 --version ?

--
Will "Coke" Coleda

[p6rt]

From @smls

For me, the command sometimes hangs and sometimes doesn't.

This is on up-do-date Rakudo​:

  ➜ uname -srm
  Linux 4.5.2-1-ARCH x86_64
 
  ➜ perl6 --version
  This is Rakudo version 2016.04-74-ga16f0a4 built on MoarVM version 2016.04
  implementing Perl 6.c.

[p6rt]

From @LLFourn

It works now!

whoever fixed it++. Close this! (and #​125758).

On Mon, May 2, 2016 at 11​:34 PM Will Coleda via RT <
perl6-bugs-followup@​perl.org> wrote​:

On Wed Apr 27 03​:02​:14 2016, lloyd.fourn@​gmail.com wrote​:

Now I'm at home I tried it on my Mac, I can confirm that​:

perl6 -e 'my $waiter = Proc​::Async.new(​:path<echo>, :args<Hello
World>).start; await start { await $waiter }'

prints Hello World and then hangs forever.

On Wed, Apr 27, 2016 at 2​:58 PM Lloyd Fournier <lloyd.fourn@​gmail.com>
wrote​:

Not sure if it's relevant here but last time I checked there is an
issues
with await and Proc​::Async on Mac.

RT #​125758 for example which looks similar to this.
On Wed, 27 Apr 2016 at 7​:08 AM, Will Coleda via RT <
perl6-bugs-followup@​perl.org> wrote​:

On Fri Sep 05 14​:44​:06 2014, elizabeth wrote​:

(since leont has been so busy with other stuff, I thought to report
the problem he found)

12​:11 * leont suspects he's observing Promise.allof spinlocking or
some such. 100% CPU usage, but no input is coming in :-/
12​:19 lizmat leont​: could you gist that ?
12​:22 leont Would need to reduce it first, but sure
13​:14 leont My spinlock seems to have gone away when I await()ed
in the same thread that created the Proc​::Async…
13​:16 lizmat leont​: interesting datapoint :-)
13​:16 wonder what jnthn would want to say about that :-)
13​:22 leont perl6 -e 'my $waiter =
Proc​::Async.new(​:path($*EXECUTABLE), :args(["helper.pl"])).start;
await start { await $waiter };'
13​:23 Let's make that easier​: perl6 -e 'my $waiter =
Proc​::Async.new(​:path("echo"), :args(<Hello World>)).start; await
start { await $waiter };'
13​:29 moritz leont++ # golfing
13​:30 leont​: could you please submit that to
rakudobugperl.org?
13​:30 leont Sure

This seems to work with no issue here. Is this ticket closable?

$ perl6 -e 'my $waiter = Proc​::Async.new(​:path("echo"), :args(<Hello
World>)).start; await start { await $waiter };'
Hello World

--
Will "Coke" Coleda

Can you include the output of sw_vers and perl6 --version ?

--
Will "Coke" Coleda

[p6rt]

From @lizmat

FWIW, I think it was 1ee27e660a8dce3ae

On 06 May 2016, at 11​:55, Lloyd Fournier <lloyd.fourn@​gmail.com> wrote​:

It works now!

whoever fixed it++. Close this! (and #​125758).

On Mon, May 2, 2016 at 11​:34 PM Will Coleda via RT <perl6-bugs-followup@​perl.org> wrote​:
On Wed Apr 27 03​:02​:14 2016, lloyd.fourn@​gmail.com wrote​:

Now I'm at home I tried it on my Mac, I can confirm that​:

perl6 -e 'my $waiter = Proc​::Async.new(​:path<echo>, :args<Hello
World>).start; await start { await $waiter }'

prints Hello World and then hangs forever.

On Wed, Apr 27, 2016 at 2​:58 PM Lloyd Fournier <lloyd.fourn@​gmail.com>
wrote​:

Not sure if it's relevant here but last time I checked there is an issues
with await and Proc​::Async on Mac.

RT #​125758 for example which looks similar to this.
On Wed, 27 Apr 2016 at 7​:08 AM, Will Coleda via RT <
perl6-bugs-followup@​perl.org> wrote​:

On Fri Sep 05 14​:44​:06 2014, elizabeth wrote​:

(since leont has been so busy with other stuff, I thought to report
the problem he found)

12​:11 * leont suspects he's observing Promise.allof spinlocking or
some such. 100% CPU usage, but no input is coming in :-/
12​:19 lizmat leont​: could you gist that ?
12​:22 leont Would need to reduce it first, but sure
13​:14 leont My spinlock seems to have gone away when I await()ed
in the same thread that created the Proc​::Async…
13​:16 lizmat leont​: interesting datapoint :-)
13​:16 wonder what jnthn would want to say about that :-)
13​:22 leont perl6 -e 'my $waiter =
Proc​::Async.new(​:path($*EXECUTABLE), :args(["helper.pl"])).start;
await start { await $waiter };'
13​:23 Let's make that easier​: perl6 -e 'my $waiter =
Proc​::Async.new(​:path("echo"), :args(<Hello World>)).start; await
start { await $waiter };'
13​:29 moritz leont++ # golfing
13​:30 leont​: could you please submit that to
rakudobugperl.org?
13​:30 leont Sure

This seems to work with no issue here. Is this ticket closable?

$ perl6 -e 'my $waiter = Proc​::Async.new(​:path("echo"), :args(<Hello
World>)).start; await start { await $waiter };'
Hello World

--
Will "Coke" Coleda

Can you include the output of sw_vers and perl6 --version ?

--
Will "Coke" Coleda

[p6rt]

From @smls

No, this one-liner...

  perl6 -e 'my $waiter = Proc​::Async.new(​:path<echo>, :args<Hello World>).start; await start { await $waiter }'

...still occasionally hangs for me on the latest Rakudo nom​:

  This is Rakudo version 2016.04-117-g7db7b46 built on MoarVM version 2016.04
  implementing Perl 6.c.

But it does appear to happen more seldomly now.
Make sure you run it many times before concluding that it works for you.

[p6rt]

From @jnthn

On Fri May 06 06​:54​:52 2016, smls75@​gmail.com wrote​:

No, this one-liner...

perl6 -e 'my $waiter = Proc​::Async.new(​:path<echo>, :args<Hello
World>).start; await start { await $waiter }'

...still occasionally hangs for me on the latest Rakudo nom​:

This is Rakudo version 2016.04-117-g7db7b46 built on MoarVM version
2016.04
implementing Perl 6.c.

But it does appear to happen more seldomly now.
Make sure you run it many times before concluding that it works for
you.

I can still reproduce it too; seems that occasionally the scheduler starts too few threads (in fact, only one, and that is tied up with the await, and so nothing processes the incoming message saying the process ended).

[p6rt]

From @jnthn

On Wed, 03 Aug 2016 12​:23​:32 -0700, jnthn@​jnthn.net wrote​:

I can still reproduce it too; seems that occasionally the scheduler
starts too few threads (in fact, only one, and that is tied up with
the await, and so nothing processes the incoming message saying the
process ended).

The new scheduler merged a couple weeks back addresses this; added a test in S17-procasync/stress.t.

[p6rt]

@jnthn - Status changed from 'open' to 'resolved'