util: drop qemu_fork()

Fortunately, qemu_fork() is no longer used since commit
a95570e3e4d6 ("io/command: use glib GSpawn, instead of open-coding
fork/exec"). (GSpawn uses posix_spawn() whenever possible instead)

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20230221124802.4103554-2-marcandre.lureau@redhat.com>

include/qemu/osdep.h

@@ -665,20 +665,6 @@ void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
  */
 char *qemu_get_pid_name(pid_t pid);
 
-/**
- * qemu_fork:
- *
- * A version of fork that avoids signal handler race
- * conditions that can lead to child process getting
- * signals that are otherwise only expected by the
- * parent. It also resets all signal handlers to the
- * default settings.
- *
- * Returns 0 to child process, pid number to parent
- * or -1 on failure.
- */
-pid_t qemu_fork(Error **errp);
-
 /* Using intptr_t ensures that qemu_*_page_mask is sign-extended even
  * when intptr_t is 32-bit and we are aligning a long long.
  */

util/oslib-posix.c

@@ -583,76 +583,6 @@ char *qemu_get_pid_name(pid_t pid)
 }
 
 
-pid_t qemu_fork(Error **errp)
-{
-    sigset_t oldmask, newmask;
-    struct sigaction sig_action;
-    int saved_errno;
-    pid_t pid;
-
-    /*
-     * Need to block signals now, so that child process can safely
-     * kill off caller's signal handlers without a race.
-     */
-    sigfillset(&newmask);
-    if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
-        error_setg_errno(errp, errno,
-                         "cannot block signals");
-        return -1;
-    }
-
-    pid = fork();
-    saved_errno = errno;
-
-    if (pid < 0) {
-        /* attempt to restore signal mask, but ignore failure, to
-         * avoid obscuring the fork failure */
-        (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
-        error_setg_errno(errp, saved_errno,
-                         "cannot fork child process");
-        errno = saved_errno;
-        return -1;
-    } else if (pid) {
-        /* parent process */
-
-        /* Restore our original signal mask now that the child is
-         * safely running. Only documented failures are EFAULT (not
-         * possible, since we are using just-grabbed mask) or EINVAL
-         * (not possible, since we are using correct arguments).  */
-        (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
-    } else {
-        /* child process */
-        size_t i;
-
-        /* Clear out all signal handlers from parent so nothing
-         * unexpected can happen in our child once we unblock
-         * signals */
-        sig_action.sa_handler = SIG_DFL;
-        sig_action.sa_flags = 0;
-        sigemptyset(&sig_action.sa_mask);
-
-        for (i = 1; i < NSIG; i++) {
-            /* Only possible errors are EFAULT or EINVAL The former
-             * won't happen, the latter we expect, so no need to check
-             * return value */
-            (void)sigaction(i, &sig_action, NULL);
-        }
-
-        /* Unmask all signals in child, since we've no idea what the
-         * caller's done with their signal mask and don't want to
-         * propagate that to children */
-        sigemptyset(&newmask);
-        if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
-            Error *local_err = NULL;
-            error_setg_errno(&local_err, errno,
-                             "cannot unblock signals");
-            error_report_err(local_err);
-            _exit(1);
-        }
-    }
-    return pid;
-}
-
 void *qemu_alloc_stack(size_t *sz)
 {
     void *ptr, *guardpage;

util/oslib-win32.c

@@ -283,15 +283,6 @@ char *qemu_get_pid_name(pid_t pid)
 }
 
 
-pid_t qemu_fork(Error **errp)
-{
-    errno = ENOSYS;
-    error_setg_errno(errp, errno,
-                     "cannot fork child process");
-    return -1;
-}
-
-
 #undef connect
 int qemu_connect_wrap(int sockfd, const struct sockaddr *addr,
                       socklen_t addrlen)