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Date: Thu, 25 May 2006 11:58:34 -0400
From: Kurt Miller <lists@intricatesoftware.com>
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Subject: close() socket deadlocks blocked threads
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Here's the other deadlock I mentioned. When a thread
is blocked waiting for data on a socket and another
thread closes the socket, the blocked thread remains
blocked indefinitely. Both kse and thr have this
issue. c_r returns with -1 errno==EBADF. Solaris
returns with -1 errno==0.

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <sys/param.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <pthread.h>

static void *
start_routine(void *arg)
{
  int sock1 = (int)arg;
  struct sockaddr remote_addr;
  char readBuf;
  int n, remote_addr_len = sizeof(struct sockaddr);

  n = recvfrom(sock1, &readBuf, 1, 0, &remote_addr, &remote_addr_len);

  if (n == -1) {
    printf("unblocked with errno = %d\n", errno);
  }

  return (0);
}

void
buildAddr4(struct sockaddr_in *addr4, int address, short port) {
  memset((char *) addr4, 0, sizeof(struct sockaddr_in));
  addr4->sin_port = htons(port);
  addr4->sin_addr.s_addr = (uint32_t) htonl(address);
  addr4->sin_family = AF_INET;
}

int
main() {
  int sock1;
  struct sockaddr addr;
  pthread_t thread1;
  void *value_ptr;

  buildAddr4((struct sockaddr_in *)&addr, 0, 0);

  if ((sock1 = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    exit(1);
  if (bind(sock1, (struct sockaddr *)&addr, sizeof(struct sockaddr_in)) != 0)
    exit(1);

  pthread_create(&thread1, NULL, start_routine, (void *)sock1);
  sleep(1);

  close(sock1);
  pthread_join(thread1, &value_ptr);

  return (0);
}