/**
* virFork:
- * @pid - a pointer to a pid_t that will receive the return value from
- * fork()
*
* Wrapper around fork() that avoids various race/deadlock conditions.
*
- * on return from virFork(), if *pid < 0, the fork failed and there is
- * no new process. Otherwise, just like fork(), if *pid == 0, it is the
- * child process returning, and if *pid > 0, it is the parent.
- *
- * Even if *pid >= 0, if the return value from virFork() is < 0, it
- * indicates a failure that occurred in the parent or child process
- * after the fork. In this case, the child process should call
- * _exit(EXIT_CANCELED) after doing any additional error reporting.
+ * Like fork(), there are several return possibilities:
+ * 1. No child was created: the return is -1, errno is set, and an error
+ * message has been reported. The semantics of virWaitProcess() recognize
+ * this to avoid clobbering the error message from here.
+ * 2. This is the parent: the return is > 0. The parent can now attempt
+ * to interact with the child (but be aware that unlike raw fork(), the
+ * child may not return - some failures in the child result in this
+ * function calling _exit(EXIT_CANCELED) if the child cannot be set up
+ * correctly).
+ * 3. This is the child: the return is 0. If this happens, the parent
+ * is also guaranteed to return.
*/
-int
-virFork(pid_t *pid)
+pid_t
+virFork(void)
{
sigset_t oldmask, newmask;
struct sigaction sig_action;
- int saved_errno, ret = -1;
-
- *pid = -1;
+ int saved_errno;
+ pid_t pid;
/*
* Need to block signals now, so that child process can safely
*/
sigfillset(&newmask);
if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
- saved_errno = errno;
virReportSystemError(errno,
"%s", _("cannot block signals"));
- goto cleanup;
+ return -1;
}
/* Ensure we hold the logging lock, to protect child processes
* from deadlocking on another thread's inherited mutex state */
virLogLock();
- *pid = fork();
+ pid = fork();
saved_errno = errno; /* save for caller */
/* Unlock for both parent and child process */
virLogUnlock();
- if (*pid < 0) {
+ if (pid < 0) {
/* attempt to restore signal mask, but ignore failure, to
- avoid obscuring the fork failure */
+ * avoid obscuring the fork failure */
ignore_value(pthread_sigmask(SIG_SETMASK, &oldmask, NULL));
virReportSystemError(saved_errno,
"%s", _("cannot fork child process"));
- goto cleanup;
- }
-
- if (*pid) {
+ errno = saved_errno;
+ } else if (pid) {
/* parent process */
/* Restore our original signal mask now that the child is
- safely running */
- if (pthread_sigmask(SIG_SETMASK, &oldmask, NULL) != 0) {
- saved_errno = errno; /* save for caller */
- virReportSystemError(errno, "%s", _("cannot unblock signals"));
- goto cleanup;
- }
- ret = 0;
+ * 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). */
+ ignore_value(pthread_sigmask(SIG_SETMASK, &oldmask, NULL));
} else {
-
/* child process */
int logprio;
size_t i;
- /* Remove any error callback so errors in child now
- get sent to stderr where they stand a fighting chance
- of being seen / logged */
+ /* Remove any error callback so errors in child now get sent
+ * to stderr where they stand a fighting chance of being seen
+ * and logged */
virSetErrorFunc(NULL, NULL);
virSetErrorLogPriorityFunc(NULL);
virLogSetDefaultPriority(logprio);
/* Clear out all signal handlers from parent so nothing
- unexpected can happen in our child once we unblock
- signals */
+ * 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 wont happen, the latter we
- expect, so no need to check return value */
-
- sigaction(i, &sig_action, NULL);
+ /* Only possible errors are EFAULT or EINVAL The former
+ * won't happen, the latter we expect, so no need to check
+ * return value */
+ ignore_value(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 */
+ /* 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) {
- saved_errno = errno; /* save for caller */
virReportSystemError(errno, "%s", _("cannot unblock signals"));
virDispatchError(NULL);
_exit(EXIT_CANCELED);
}
- ret = 0;
}
-
-cleanup:
- if (ret < 0)
- errno = saved_errno;
- return ret;
+ return pid;
}
/*
int tmpfd;
char *binarystr = NULL;
const char *binary = NULL;
- int forkRet, ret;
+ int ret;
struct sigaction waxon, waxoff;
gid_t *groups = NULL;
int ngroups;
if ((ngroups = virGetGroupList(cmd->uid, cmd->gid, &groups)) < 0)
goto cleanup;
- forkRet = virFork(&pid);
+ pid = virFork();
if (pid < 0) {
goto cleanup;
}
if (pid) { /* parent */
- if (forkRet < 0) {
- goto cleanup;
- }
-
VIR_FORCE_CLOSE(null);
if (cmd->outfdptr && *cmd->outfdptr == -1) {
VIR_FORCE_CLOSE(pipeout[1]);
/* child */
ret = EXIT_CANCELED;
- if (forkRet < 0) {
- /* The fork was successful, but after that there was an error
- * in the child (which was already logged).
- */
- goto fork_error;
- }
-
openmax = sysconf(_SC_OPEN_MAX);
if (openmax < 0) {
virReportSystemError(errno, "%s",
if (pid > 0) {
if (cmd->pidfile && (virPidFileWritePath(cmd->pidfile, pid) < 0)) {
- kill(pid, SIGTERM);
- usleep(500*1000);
- kill(pid, SIGTERM);
- virReportSystemError(errno,
- _("could not write pidfile %s for %d"),
- cmd->pidfile, pid);
+ if (virProcessKillPainfully(pid, true) >= 0)
+ virReportSystemError(errno,
+ _("could not write pidfile %s for %d"),
+ cmd->pidfile, pid);
goto fork_error;
}
_exit(EXIT_SUCCESS);
return -1;
}
-int
-virFork(pid_t *pid)
+pid_t
+virFork(void)
{
- *pid = -1;
errno = ENOTSUP;
return -1;
* @exitstatus: optional status collection
* @raw: whether to pass non-normal status back to caller
*
- * Wait for a child process to complete. If @exitstatus is NULL, then the
- * child must exit normally with status 0. Otherwise, if @raw is false,
- * the child must exit normally, and @exitstatus will contain the final
- * exit status (no need for the caller to use WEXITSTATUS()). If @raw is
- * true, then the result of wait() is returned in @exitstatus, and the
- * caller must use WIFEXITED() and friends to decipher the child's status.
+ * Wait for a child process to complete. If @pid is -1, do nothing, but
+ * return -1 (useful for error cleanup, and assumes an earlier message was
+ * already issued). All other pids issue an error message on failure.
+ *
+ * If @exitstatus is NULL, then the child must exit normally with status 0.
+ * Otherwise, if @raw is false, the child must exit normally, and
+ * @exitstatus will contain the final exit status (no need for the caller
+ * to use WEXITSTATUS()). If @raw is true, then the result of waitpid() is
+ * returned in @exitstatus, and the caller must use WIFEXITED() and friends
+ * to decipher the child's status.
*
* Returns 0 on a successful wait. Returns -1 on any error waiting for
* completion, or if the command completed with a status that cannot be
int status;
if (pid <= 0) {
- virReportSystemError(EINVAL, _("unable to wait for process %lld"),
- (long long) pid);
+ if (pid != -1)
+ virReportSystemError(EINVAL, _("unable to wait for process %lld"),
+ (long long) pid);
return -1;
}
return -1;
}
- ret = virFork(&child);
-
- if (ret < 0 || child < 0) {
- if (child == 0)
- _exit(EXIT_CANCELED);
-
- /* parent */
- virProcessAbort(child);
+ if ((child = virFork()) < 0)
goto cleanup;
- }
if (child == 0) {
VIR_FORCE_CLOSE(errfd[0]);
projects / thirdparty / libvirt.git / commitdiff
