Messages in this thread | | | Date | Mon, 10 May 2004 22:26:36 +0100 | From | Andre Ben Hamou <> | Subject | Multithread select() bug |
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Here's the scenario...
- parent thread P creates a connected socket pair S[0, 1] - P spawns a child thread C and passes it S - C selects on S[0] - P closes S[0]
As I understand the semantics of the select call, C should now return immediately in response to the closure (and it does on Mac OS X). However, the following test code behaves otherwise for the two test cases I've tried (2.4.21 and 2.6.5). Compilation command used: 'gcc foobar.c -lpthread'.
Cheers,
Andre Ben Hamou Imperial College London
--- BEGIN TEST CODE (foobar.c)---
#include <assert.h> // assert #include <pthread.h> // pthread_create #include <sys/select.h> // select #include <sys/types.h> // socketpair #include <sys/socket.h> // socketpair #include <unistd.h> // sleep #include <stdio.h> // printf
void *threadFuntion (void *sockets) { int socket = ((int *)sockets)[0]; struct timeval timeout = {tv_sec: 5, tv_usec: 0};
// Allocate a file descriptor set with the passed socket fd_set fds; FD_ZERO (&fds); FD_SET (socket, &fds);
// Select to read / register exceptions on the FD set select (socket + 1, &fds, NULL, &fds, &timeout);
return NULL; }
int main (void) { int sockets[2]; pthread_t thread;
// Create a connected pair of sockets assert (socketpair (PF_UNIX, SOCK_STREAM, 0, sockets) != -1); printf ("sockets: {%i, %i}\n", sockets[0], sockets[1]);
// Create a POSIX thread // - use the default configuration // - invoke 'threadFunction' as the root function of the thread // - pass the socket array to 'threadFunction' assert (pthread_create (&thread, NULL, threadFuntion, sockets) == 0);
// Wait for a second and then close the socket being selected on sleep (1); assert (close (sockets[0]) == 0); printf ("Socket closed\n");
// Wait for the thread to exit - SHOULD BE ~ INSTANTANEOUS assert (pthread_join (thread, NULL) == 0); printf ("Thread joined\n");
assert (close (sockets[1]) == 0); return 0; }
--- END TEST CODE ---
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