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Re: Cancelling threads
- To: Ollie Leahy <ollie at mpt dot ie>, pthreads-win32 at sources dot redhat dot com
- Subject: Re: Cancelling threads
- From: reentrant <reentrant at yahoo dot com>
- Date: Tue, 10 Apr 2001 13:10:31 -0700 (PDT)
For this particular case, in my experience the accept() returns (with some
error) if another thread close()s the socket returned by bind().
--- Ollie Leahy <ollie@mpt.ie> wrote:
>
> Reading the FAQ I'm unsure about whether snapshots after
> snapshot-1999-11-02 implement asynchronous thread cancelling.
>
> The FAQ makes the following statement:
>
> Snapshot 99-11-02 or earlier only partially supports asynchronous
> cancellation.
> If the thread you're trying to cancel is blocked (for instance, it could be
> waiting for data from the network), it will only get cancelled when it
> unblocks
> (when the data arrives). Unfortunately, there is no way to do so from
> outside the thread.
>
>
> Does this mean that snapshots after 99-11-02 do completely support
> asynchronous cancel? I'm using pthreads-2000-12-29.exe and
> the test program below blocks in the accept call and is not cancelled.
> The FAQ seems to imply that the thread will be terminated in libraries
> built after 1999-11-02, either:
>
> a) This interpretation of the FAQ is not correct and there is
> no way to terminate a thread that is blocked in a system call.
>
> or
>
> b) There something else I need to do in order to terminate
> the thread blocking in accept()
>
> Can you tell me which is the case?
>
> For what it's worth, the thread is terminated when the same program
> is run under Linux.
>
> Thanks,
> Ollie Leahy
>
>
>
>
>
>
> #include <stdio.h>
> #ifndef _WIN32
> #include <stdlib.h>
> #include <sys/types.h>
> #include <sys/socket.h>
> #include <netinet/in.h>
> #include <unistd.h>
> #include <string.h>
> #else
> #include <windows.h>
> #include <winsock.h>
> #define sleep(n) Sleep(n * 1000)
> #define close(n) closesocket(n)
> #endif
>
> #include <pthread.h>
>
>
>
> pthread_t t1;
> pthread_t t2;
>
> void *
> thread1(void *dummy)
> {
> int oldtype;
> int ns, s;
> struct sockaddr_in sin;
> int len;
>
> pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &oldtype);
> if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
> printf("socket error");
> return NULL;
> }
> memset((char *)&sin, 0, sizeof(sin));
> sin.sin_family = AF_INET;
> sin.sin_addr.s_addr = INADDR_ANY;
> sin.sin_port = htons(7777);
> if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
> printf("bind failed.\n");
> return NULL;
> }
> if (listen(s,8)) {
> printf("listen error");
> return NULL;
> }
> printf("Ready to accept a connection\n");
> len = sizeof(struct sockaddr_in);
> if ((ns = accept(s, (struct sockaddr *)&sin, &len)) < 1) {
> printf("accept error");
> return NULL;
> }
> printf("Thread finishing normally.\n");
> close(s);
> close(ns);
> return NULL;
> }
>
>
>
> int
> main(int ac, char ** av)
> {
> #if defined (_WIN32)
> WSADATA junk;
> #endif
> void * rValue = NULL;
>
> #if defined (_WIN32)
>
> if (WSAStartup(MAKEWORD(2, 0), &junk) != 0) {
> return -1;
> }
> #endif
>
>
> if (pthread_create(&t1, 0, thread1, 0)) {
> printf("pthread_create() thread1 failed\n");
> return -1;
> }
>
> /*
> * Give the thread time to block in accept()
> */
> sleep(10);
> printf("Canceling thread.\n");
> pthread_cancel(t1);
> pthread_join(t1, &rValue);
>
>
>
> #if defined (_WIN32)
> WSACleanup();
> #endif
>
> return 0;
> }
>
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