Re: How to implement Canceleable spawn() from parent
On 7/1/20 2:41 AM, aberba wrote: On Tuesday, 30 June 2020 at 14:43:40 UTC, Steven Schveighoffer wrote: On 6/30/20 10:15 AM, Simen Kjærås wrote: [...] My thinking is I don't want regular consumers using the package to think about the technicality of thread_joinAll() at all. Thinking about putting it in a mixin like: mixin KeepRunning; Or something How about main() starts a thread that starts all the other threads? Then, thread_joinAll() would go inside the non-main :) thread. However, Steve is right: When main() exits, all threads will and should exit. Ali
Re: How to implement Canceleable spawn() from parent
On Tuesday, 30 June 2020 at 14:43:40 UTC, Steven Schveighoffer wrote: On 6/30/20 10:15 AM, Simen Kjærås wrote: [...] My thinking is I don't want regular consumers using the package to think about the technicality of thread_joinAll() at all. Thinking about putting it in a mixin like: mixin KeepRunning; Or something
Re: How to implement Canceleable spawn() from parent
On 6/30/20 10:15 AM, Simen Kjærås wrote:
On Tuesday, 30 June 2020 at 13:44:38 UTC, aberba wrote:
On Tuesday, 30 June 2020 at 12:48:32 UTC, Simen Kjærås wrote:
On Tuesday, 30 June 2020 at 08:15:54 UTC, aberba wrote:
On Tuesday, 30 June 2020 at 00:33:41 UTC, Ali Çehreli wrote:
On 6/29/20 4:34 PM, aberba wrote:
> So with this, without the Thread.sleep() to block main from
exiting, the
> spawned thread will terminate immediately.
You can call core.thread.thread_joinAll at the end of main.
So I tried that initially but my (){ writeln(...) } wasn't printing
anything in console. Could that be related to stdout buffering? The
program kept running though.
So I guess the error is elsewhere, but I'm not sure where and how.
Yeah, you're right. I changed receiveTimeout() to receive() to try
something and forgot to change it back.
Jeez, I hate myself.
Thanks.
So how can I now hide the core.thread.thread_joinAll so the library
user doesn't have to type it themselves in main() ? I don't see how
that can be done.
__gshared Tid mainTid;
static this() {
if (mainTid.tupleof[0] is null) {
mainTid = thisTid;
}
}
static ~this() {
if (thisTid == mainTid) {
thread_joinAll();
}
}
First, you can just use shared static dtor, as this runs once at the end
of the program. At the very least, you can run the setting of mainTid in
a shared constructor to avoid the race conditions (also no need to check
if its set already).
Second, I realized, thread_joinAll is already being done by the runtime:
https://github.com/dlang/druntime/blob/67618bd2dc8905ad5dee95f3329109aebd839b74/src/rt/dmain2.d#L226
So the question really becomes -- why is it necessary to call
thread_joinAll in main?
It's because the main thread's TLS static destructor is closing the
owner mailbox, which is sending a message to all the threads that the
owner is terminated, causing your threads to exit immediately.
See here:
https://github.com/dlang/phobos/blob/268b56be494cc4f76da54a66a6960fa7e527c4ed/std/concurrency.d#L223
Honestly though, I think this is the correct behavior -- if you exit
main, you are expecting the program to not hang indefinitely.
-Steve
Re: How to implement Canceleable spawn() from parent
On Tuesday, 30 June 2020 at 13:44:38 UTC, aberba wrote:
On Tuesday, 30 June 2020 at 12:48:32 UTC, Simen Kjærås wrote:
On Tuesday, 30 June 2020 at 08:15:54 UTC, aberba wrote:
On Tuesday, 30 June 2020 at 00:33:41 UTC, Ali Çehreli wrote:
On 6/29/20 4:34 PM, aberba wrote:
> So with this, without the Thread.sleep() to block main from
exiting, the
> spawned thread will terminate immediately.
You can call core.thread.thread_joinAll at the end of main.
So I tried that initially but my (){ writeln(...) } wasn't
printing anything in console. Could that be related to stdout
buffering? The program kept running though.
So I guess the error is elsewhere, but I'm not sure where and
how.
Yeah, you're right. I changed receiveTimeout() to receive() to
try something and forgot to change it back.
Jeez, I hate myself.
Thanks.
So how can I now hide the core.thread.thread_joinAll so the
library user doesn't have to type it themselves in main() ? I
don't see how that can be done.
__gshared Tid mainTid;
static this() {
if (mainTid.tupleof[0] is null) {
mainTid = thisTid;
}
}
static ~this() {
if (thisTid == mainTid) {
thread_joinAll();
}
}
The above code does the trick.
So, what does it do? __gshared means 'this variable is accessible
to all threads'. static this() runs upon creation of any thread
including the main thread. Since the main thread will run first*,
it gets to store its Tid in mainTid, and every other thread will
see a populated mainTid and leave it alone. In the module
destructor, which runs after main(), we call thread_joinAll() iff
we're the main thread.
Now, why should you not do this? Well first, instead of getting a
tidy crash you get a process that doesn't end. Second, there's
the race conditions described below. Third, there's the principle
of least astonishment. D programmers expect that when main()
returns, the program will exit shortly(ish), while this zombie
could continue running indefinitely.
--
Simen
*I'm pretty sure this is possibly wrong, if a module constructor
spawns a new thread. There's also a possible race condition where
newly spawned modules may conceivably not see a properly
initialized mainTid.
Re: How to implement Canceleable spawn() from parent
On 6/30/20 9:44 AM, aberba wrote: On Tuesday, 30 June 2020 at 12:48:32 UTC, Simen Kjærås wrote: So I guess the error is elsewhere, but I'm not sure where and how. Yeah, you're right. I changed receiveTimeout() to receive() to try something and forgot to change it back. Jeez, I hate myself. Thanks. So how can I now hide the core.thread.thread_joinAll so the library user doesn't have to type it themselves in main() ? I don't see how that can be done. I assume you need something more than thread_joinAll, because you need to stop all the threads from executing also. So wrapping this up into a single call would be what you use (it's OK to ask the user to clean up a library manually). -Steve
Re: How to implement Canceleable spawn() from parent
On Tuesday, 30 June 2020 at 12:48:32 UTC, Simen Kjærås wrote:
On Tuesday, 30 June 2020 at 08:15:54 UTC, aberba wrote:
On Tuesday, 30 June 2020 at 00:33:41 UTC, Ali Çehreli wrote:
On 6/29/20 4:34 PM, aberba wrote:
> So with this, without the Thread.sleep() to block main from
exiting, the
> spawned thread will terminate immediately.
You can call core.thread.thread_joinAll at the end of main.
So I tried that initially but my (){ writeln(...) } wasn't
printing anything in console. Could that be related to stdout
buffering? The program kept running though.
So I guess the error is elsewhere, but I'm not sure where and
how.
Yeah, you're right. I changed receiveTimeout() to receive() to
try something and forgot to change it back.
Jeez, I hate myself.
Thanks.
So how can I now hide the core.thread.thread_joinAll so the
library user doesn't have to type it themselves in main() ? I
don't see how that can be done.
Re: How to implement Canceleable spawn() from parent
On Tuesday, 30 June 2020 at 08:15:54 UTC, aberba wrote:
On Tuesday, 30 June 2020 at 00:33:41 UTC, Ali Çehreli wrote:
On 6/29/20 4:34 PM, aberba wrote:
> So with this, without the Thread.sleep() to block main from
exiting, the
> spawned thread will terminate immediately.
You can call core.thread.thread_joinAll at the end of main.
So I tried that initially but my (){ writeln(...) } wasn't
printing anything in console. Could that be related to stdout
buffering? The program kept running though.
Seems weird. This works great on my machine:
import core.time : Duration, msecs;
import core.thread : Thread, thread_joinAll;
import std.concurrency : spawn, Tid, send, receiveTimeout;
import std.stdio : writeln;
private struct IntervalStop {}
Tid setInterval(Duration dur, void function() fn) {
return spawn((Duration d, void function() f){
while (!receiveTimeout(d, (IntervalStop s){})) {
f();
}
}, dur, fn);
}
void stopInterval(Tid tid) {
tid.send(IntervalStop());
}
void main() {
auto a = setInterval(1000.msecs, (){ writeln("Hello from
spawned thread A"); });
// Stop it before it happens
stopInterval(a);
Thread.sleep(2000.msecs);
auto b = setInterval(1000.msecs, (){ writeln("Hello from
spawned thread B"); });
// Let this one run a little
Thread.sleep(2500.msecs);
stopInterval(b);
auto c = setInterval(1000.msecs, (){ writeln("Hello from
spawned thread C"); });
// Sending the wrong message doesn't make it happen or stop
prematurely
c.send("Stop this at once!");
Thread.sleep(2500.msecs);
stopInterval(c);
thread_joinAll();
}
So I guess the error is elsewhere, but I'm not sure where and how.
--
Simen
Re: How to implement Canceleable spawn() from parent
On Tuesday, 30 June 2020 at 00:33:41 UTC, Ali Çehreli wrote:
On 6/29/20 4:34 PM, aberba wrote:
> So with this, without the Thread.sleep() to block main from
exiting, the
> spawned thread will terminate immediately.
You can call core.thread.thread_joinAll at the end of main.
So I tried that initially but my (){ writeln(...) } wasn't
printing anything in console. Could that be related to stdout
buffering? The program kept running though.
Another way would be to wait for a worker's exit by looking for
LinkTerminated but you need to start the thread with
spawnLinked:
Read that too, but doesn't seem like the desired behavior I want.
So here's the thing, unlike JavaScript, the D behavior seems to
be like a while(bool){} has to be placed directly within the
scope of main. Was thinking as long my while loop in
setInterval() was running, spawn() will be kept alive.
It seem both vibe.d and arsd have a similar setInterval()
implementation and they both require using their event loop to
keep the program alive.
In my case, wanted setInterval() to behave like it's own event
loop without placing it in a while(bool){} loop in main()
Re: How to implement Canceleable spawn() from parent
On 6/29/20 4:34 PM, aberba wrote: > So with this, without the Thread.sleep() to block main from exiting, the > spawned thread will terminate immediately. You can call core.thread.thread_joinAll at the end of main. Another way would be to wait for a worker's exit by looking for LinkTerminated but you need to start the thread with spawnLinked: http://ddili.org/ders/d.en/concurrency.html#ix_concurrency.LinkTerminated Ali
Re: How to implement Canceleable spawn() from parent
On Sunday, 28 June 2020 at 14:23:01 UTC, Stanislav Blinov wrote: On Sunday, 28 June 2020 at 13:29:08 UTC, aberba wrote: [...] The error you're getting is because you're passing a pointer to a delegate instead of a delegate. [...] So with this, without the Thread.sleep() to block main from exiting, the spawned thread will terminate immediately. How do I keep it from happening? Keep it running continuously? From the docs, it says OwnerTerminated exception gets thrown when the sending thread (e.i. main) is terminated. Thrown on calls to receive if the thread that spawned the receiving thread has terminated and no more messages exist.
Re: How to implement Canceleable spawn() from parent
I'm doing this in an X11 application in order to send a timer
event every 100 milliseconds to the main event queue.
class Application
{
shared private bool s_tick;
void clock_task (shared X11.Display* disp, X11.Atom atom,
X11.Window win)
{
for (;;)
{
try
{
receiveTimeout (100.msecs);
if (disp && atomicLoad(s_tick))
{
// disable ticking until it is allowed again at the end
of the event loop
atomicStore(s_tick, false);
X11.XClientMessageEvent event;
event.type = X11.ClientMessage;
event.window = win;
event.message_type = atom;
event.format = 32;
event.data.l = [0, 0, 0, 0, 0];
X11.XSendEvent (cast (X11.Display*) disp, win, 0, 0,
cast(X11.XEvent*));
X11.XFlush (cast (X11.Display*) disp);
}
}
catch (Throwable)
{
return;
}
}
}
this ()
{
...
spawn (_task, cast(shared)x11Display, x11SigClockAtom,
_x11_proxyWindow);
}
run ()
{
while (true)
{
...
// event processing starts here: read in X11 event and
convert it to a wit Event
X11.XEvent x11_event;
X11.XNextEvent (_x11.display, _event);
...
atomicStore(s_tick, true);
}
}
}
Re: How to implement Canceleable spawn() from parent
On 6/28/20 4:08 PM, aberba wrote: So I checked receiveTimeout() when I was looking for what I could use. I wish there was an example in the docs. https://dlang.org/library/std/concurrency/receive_timeout.html I have an example of it: http://ddili.org/ders/d.en/concurrency.html#ix_concurrency.receiveTimeout Ali
Re: How to implement Canceleable spawn() from parent
On Sunday, 28 June 2020 at 23:39:07 UTC, Stanislav Blinov wrote: On Sunday, 28 June 2020 at 23:02:26 UTC, aberba wrote: I believe this: StopWatch sw; sw.start; works becuse D structs are initialized by default, right? I've never actually done it this way. Little details. Yup. You can also do a auto sw = StopWatch(AutoStart.yes); and not have to call `start` explicitly. Interesting. I should look into Phobos more.
Re: How to implement Canceleable spawn() from parent
On Sunday, 28 June 2020 at 23:02:26 UTC, aberba wrote: I believe this: StopWatch sw; sw.start; works becuse D structs are initialized by default, right? I've never actually done it this way. Little details. Yup. You can also do a auto sw = StopWatch(AutoStart.yes); and not have to call `start` explicitly.
Re: How to implement Canceleable spawn() from parent
On Sunday, 28 June 2020 at 23:02:26 UTC, aberba wrote: On Sunday, 28 June 2020 at 14:23:01 UTC, Stanislav Blinov wrote: On Sunday, 28 June 2020 at 13:29:08 UTC, aberba wrote: Thanks. I believe this: StopWatch sw; sw.start; works becuse D structs are initialized by default, right? I've never actually done it this way. Little details. So I checked receiveTimeout() when I was looking for what I could use. I wish there was an example in the docs. https://dlang.org/library/std/concurrency/receive_timeout.html
Re: How to implement Canceleable spawn() from parent
On Sunday, 28 June 2020 at 14:23:01 UTC, Stanislav Blinov wrote: On Sunday, 28 June 2020 at 13:29:08 UTC, aberba wrote: Thanks. I believe this: StopWatch sw; sw.start; works becuse D structs are initialized by default, right? I've never actually done it this way. Little details.
Re: How to implement Canceleable spawn() from parent
On Sunday, 28 June 2020 at 13:29:08 UTC, aberba wrote:
Getting error:
Error: template std.concurrency.spawn cannot deduce function
from argument types !()(void delegate(Tid id) @system, Tid),
candidates are:
/usr/include/dmd/phobos/std/concurrency.d(460,5):
spawn(F, T...)(F fn, T args)
with F = void delegate(Tid) @system,
T = (Tid)
must satisfy the following constraint:
isSpawnable!(F, T)
The error you're getting is because you're passing a pointer to a
delegate instead of a delegate.
Tid id = spawn(, milliseconds, );
^ here
But fixing that still won't compile, because when you want to
pass a delegate to `spawn`, it needs to be a shared delegate.
If I understood your intent correctly, here's how you can do it:
import std.stdio : writeln;
import std.concurrency;
import core.thread.osthread : Thread;
import std.datetime.stopwatch;
auto setInterval(long milliseconds, void function() callback)
{
static void worker(Duration d, void function() cb)
{
writeln("Starting ", thisTid, "...");
bool done = false;
StopWatch sw;
sw.start;
while (true)
{
// wait for messages for a timespan of at least `d`
receiveTimeout(
d,
(string text) {
writeln("Received string: ", text);
if (text == "cancel")
done = true;
});
if (done)
break;
// a non-cancelling message might've been received
before timeout,
// so test if it's really time for the callback
if (sw.peek >= d)
{
cb();
sw.reset;
}
}
}
Tid id = spawn(, milliseconds.msecs, callback);
return id;
}
void stopInterval(Tid tid) {
send(tid, "cancel");
}
void main()
{
auto tid = setInterval(1000, { writeln("tick"); });
Thread.sleep(2.seconds);
send(tid, "not cancel");
Thread.sleep(5.seconds);
stopInterval(tid);
}
How to implement Canceleable spawn() from parent
Trying to implement a setInterval() that I can cancel using:
Tid tid = setInterval(2000, (){ writeln("hello");})
And then I can do:
stopInterval(tid);
With something like this:
stopInterval(Tid tid) {
send(tid, "cancel");
}
import std.stdio : writeln;
import std.concurrency : receive, spawn, thisTid, Tid;
auto setInterval(long milliseconds, void delegate() callback)
{
auto worker(long mls, void delegate() cb)
{
import core.thread.osthread : Thread;
import std.datetime : seconds, msecs;
writeln("Starting ", thisTid, "...");
bool done = false;
receive((string text) {
writeln("Received string: ", text);
done = true;
});
do
{
// or receive() comes here?
Thread.sleep(mls.msecs);
cb();
}
while (!done);
}
// I guess issue is with the callback
Tid id = spawn(, milliseconds, );
return id;
}
Getting error:
Error: template std.concurrency.spawn cannot deduce function from
argument types !()(void delegate(Tid id) @system, Tid),
candidates are:
/usr/include/dmd/phobos/std/concurrency.d(460,5):spawn(F,
T...)(F fn, T args)
with F = void delegate(Tid) @system,
T = (Tid)
must satisfy the following constraint:
isSpawnable!(F, T)
Am I even using the right tool here?
