Hello everyone,

I've been getting the error message "Interrupted System Call" a lot lately, ever since I started using threads in D. It appears whenever one of the threads in my application creates and uses an associative array while another thread executes a blocking system call such as readln or receive on sockets. Here is an example:

=====================

import std.stdio;
import std.thread;

int readlnfunc (void* arg)
{
	readln();
	return 0;
}

void main ()
{
	(new Thread (&readlnfunc, null)).start();

	while (true) {
		int[int] aa;
		aa[0] = 0;
	}
}

=====================

I'm using dmd 1.033 on Ubuntu 8.04.

This looks like a bug to me; I don't know how to fix it or work around it either. Sometimes the error doesn't throw up an exception, but it still prevents me from using some other functions:

=====================

import std.socket;
import std.stdio;
import std.thread;

int serverfunc (void* arg)
{
	Socket listener = new TcpSocket ();
	listener.bind (new InternetAddress(1234));
	listener.listen(10);
	Socket socket = listener.accept ();
	assert (socket.isAlive);

	ubyte[512] buf;
	int bytes = socket.receive(buf);
	writefln ("Server: Received %d bytes.", bytes);

	socket.shutdown (SocketShutdown.BOTH);
	socket.close;
	listener.close;
	return 0;
}

int clientfunc (void* arg)
{
	Socket socket = new TcpSocket(new InternetAddress("127.0.0.1", 1234));
	assert (socket.isAlive);

	ubyte[512] buf;
	int bytes = socket.receive(buf);
	writefln ("Client: Received %d bytes.", bytes);

	socket.shutdown (SocketShutdown.BOTH);
	socket.close();
	return 0;
}

void main ()
{
	(new Thread (&serverfunc, null)).start();
	(new Thread (&clientfunc, null)).start();

	for (int i = 0; i < 100000; ++i) {
		int[int] aa;
		aa[0] = 0;
		Thread.yield();
	}
}

=====================

A simple server-client connection and both call receive(). Both these calls return Socket.ERROR, and the error disappears when I take out the aa in main. Optionally, if I put the aa in another extra thread and let the loop run before the client connects, accept() from the server will spit out an "Interrupted System Call".

Does anyone have any suggestions on how to fix or work around this problem? I couldn't find anyone else who had it.

-Peter

"Peter Neubauer" <peterneubauer2@gmail.com> wrote in message news:g66s1f$120h$1@digitalmars.com...
> Hello everyone,
>
> I've been getting the error message "Interrupted System Call" a lot lately, ever since I started using threads in D. It appears whenever one of the threads in my application creates and uses an associative array while another thread executes a blocking system call such as readln or receive on sockets. Here is an example:
>
> =====================
>
> import std.stdio;
> import std.thread;
>
> int readlnfunc (void* arg)
> {
> readln();
> return 0;
> }
>
> void main ()
> {
> (new Thread (&readlnfunc, null)).start();
>
> while (true) {
> int[int] aa;
> aa[0] = 0;
> }
> }
>
> =====================
>
> I'm using dmd 1.033 on Ubuntu 8.04.
>
> This looks like a bug to me; I don't know how to fix it or work around it either. Sometimes the error doesn't throw up an exception, but it still prevents me from using some other functions:
>
> =====================
>
> import std.socket;
> import std.stdio;
> import std.thread;
>
> int serverfunc (void* arg)
> {
> Socket listener = new TcpSocket ();
> listener.bind (new InternetAddress(1234));
> listener.listen(10);
> Socket socket = listener.accept ();
> assert (socket.isAlive);
>
> ubyte[512] buf;
> int bytes = socket.receive(buf);
> writefln ("Server: Received %d bytes.", bytes);
>
> socket.shutdown (SocketShutdown.BOTH);
> socket.close;
> listener.close;
> return 0;
> }
>
> int clientfunc (void* arg)
> {
> Socket socket = new TcpSocket(new InternetAddress("127.0.0.1", 1234));
> assert (socket.isAlive);
>
> ubyte[512] buf;
> int bytes = socket.receive(buf);
> writefln ("Client: Received %d bytes.", bytes);
>
> socket.shutdown (SocketShutdown.BOTH);
> socket.close();
> return 0;
> }
>
> void main ()
> {
> (new Thread (&serverfunc, null)).start();
> (new Thread (&clientfunc, null)).start();
>
> for (int i = 0; i < 100000; ++i) {
> int[int] aa;
> aa[0] = 0;
> Thread.yield();
> }
> }
>
> =====================
>
> A simple server-client connection and both call receive(). Both these calls return Socket.ERROR, and the error disappears when I take out the aa in main. Optionally, if I put the aa in another extra thread and let the loop run before the client connects, accept() from the server will spit out an "Interrupted System Call".
>
> Does anyone have any suggestions on how to fix or work around this problem? I couldn't find anyone else who had it.
>
> -Peter

See the "linux system calls are canceled by D GC" thread on digitalmars.D.bugs.  I think this is what you're experiencing.

Peter Neubauer wrote:
> Hello everyone,
> 
> I've been getting the error message "Interrupted System Call" a lot lately, ever since I started using threads in D. It appears whenever one of the threads in my application creates and uses an associative array while another thread executes a blocking system call such as readln or receive on sockets.

I imagine you're using Phobos?  Phobos omits some signal flags to tell the OS to try and resume system calls if they are interrupted by a garbage collection cycle.  Tango sets them properly.


Sean

Sean Kelly wrote:
> Peter Neubauer wrote:
>> Hello everyone,
>>
>> I've been getting the error message "Interrupted System Call" a lot lately, ever since I started using threads in D. It appears whenever one of the threads in my application creates and uses an associative array while another thread executes a blocking system call such as readln or receive on sockets.
> 
> I imagine you're using Phobos?  Phobos omits some signal flags to tell the OS to try and resume system calls if they are interrupted by a garbage collection cycle.  Tango sets them properly.
> 
> 
> Sean

Thanks for your answers, switching to Tango has solved my problem.

-Peter