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08d8015750
There is a race condition in old libc in fork(). The result was that 'end' was sometimes printed twice. This did not happen with glibc-2.32.
144 lines
2.6 KiB
C
144 lines
2.6 KiB
C
#include <stdio.h>
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#include <pthread.h>
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#include <semaphore.h>
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#include <signal.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <setjmp.h>
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static volatile int run = 1;
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static sem_t sem;
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static sem_t sem_child;
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static void
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add (int n)
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{
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int i;
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int arr[n];
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for (i = 0; i < n; i++) {
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arr[i]++;
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}
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memset (&arr[0], 0, n * sizeof(int));
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}
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static void *
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high_load (void *unused)
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{
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while (run) {
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add(10);
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add(20);
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}
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return NULL;
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}
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static void *
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do_signal (void *unused)
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{
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while (run) {
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kill (getpid(), SIGUSR1);
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while (sem_wait(&sem) < 0 && errno == EINTR);
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}
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return NULL;
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}
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static void *
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do_fork (void *unused)
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{
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pid_t pid;
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while (run) {
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switch ((pid = fork())) {
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case 0:
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add(1000);
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add(2000);
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exit(0);
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break;
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case -1:
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return NULL;
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default:
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while (sem_wait(&sem_child) < 0 && errno == EINTR);
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wait(NULL);
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break;
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}
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}
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return NULL;
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}
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static void signal_handler(int sig)
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{
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add(10);
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add(20);
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sem_post (&sem);
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}
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static void child_handler(int sig)
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{
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add(10);
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add(20);
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sem_post (&sem_child);
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}
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int
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main (void)
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{
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int i;
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pthread_t id1, id2, id3;
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struct sigaction act;
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sigjmp_buf sj;
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sigset_t m;
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time_t end;
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memset (&act, 0, sizeof (act));
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act.sa_handler = signal_handler;
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act.sa_flags = 0;
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sigemptyset (&act.sa_mask);
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sigaction (SIGUSR1, &act, NULL);
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act.sa_handler = child_handler;
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sigaction (SIGCHLD, &act, NULL);
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printf ("start\n"); fflush(stdout);
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sem_init (&sem, 0, 0);
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sem_init (&sem_child, 0, 0);
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pthread_create(&id1, NULL, high_load, NULL);
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pthread_create(&id2, NULL, do_signal, NULL);
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#if !defined(__APPLE__)
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pthread_create(&id3, NULL, do_fork, NULL);
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#endif
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/* sleep does not work !!! */
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end = time(NULL) + 2;
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while (time(NULL) < end) ;
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run = 0;
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pthread_join(id1, NULL);
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pthread_join(id2, NULL);
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#if !defined(__APPLE__)
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pthread_join(id3, NULL);
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#endif
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sem_destroy (&sem);
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sem_destroy (&sem_child);
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printf ("end\n"); fflush(stdout);
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sigemptyset (&m);
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sigprocmask (SIG_SETMASK, &m, NULL);
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if (sigsetjmp (sj, 0) == 0)
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{
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sigaddset (&m, SIGUSR1);
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sigprocmask (SIG_SETMASK, &m, NULL);
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siglongjmp (sj, 1);
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printf ("failed");
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return 1;
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}
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sigprocmask (SIG_SETMASK, NULL, &m);
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if (!sigismember (&m, SIGUSR1))
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printf ("failed");
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return 0;
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}
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