qemu: Faster response time to qemu startup errors

The below patch decreases the response time of libvirt to errors reported by Qemu upon startup by checking whether the qemu process is still alive while polling for the local socket to show up.

This patch also introduces a special handling of signal for the Win32 part of virKillProcess.

src/qemu/qemu_monitor.c

@@ -247,7 +247,7 @@ qemuMonitorUnwatch(void *monitor)
 }
 
 static int
-qemuMonitorOpenUnix(const char *monitor)
+qemuMonitorOpenUnix(const char *monitor, pid_t cpid)
 {
     struct sockaddr_un addr;
     int monfd;
@@ -274,7 +274,8 @@ qemuMonitorOpenUnix(const char *monitor)
         if (ret == 0)
             break;
 
-        if (errno == ENOENT || errno == ECONNREFUSED) {
+        if ((errno == ENOENT || errno == ECONNREFUSED) &&
+            virKillProcess(cpid, 0) == 0) {
             /* ENOENT       : Socket may not have shown up yet
              * ECONNREFUSED : Leftover socket hasn't been removed yet */
             continue;
@@ -691,7 +692,7 @@ qemuMonitorOpen(virDomainObjPtr vm,
     switch (config->type) {
     case VIR_DOMAIN_CHR_TYPE_UNIX:
         mon->hasSendFD = 1;
-        mon->fd = qemuMonitorOpenUnix(config->data.nix.path);
+        mon->fd = qemuMonitorOpenUnix(config->data.nix.path, vm->pid);
         break;
 
     case VIR_DOMAIN_CHR_TYPE_PTY:

src/util/util.c

@@ -2010,7 +2010,7 @@ int virKillProcess(pid_t pid, int sig)
          * TerminateProcess is more or less equiv to SIG_KILL, in that
          * a process can't trap / block it
          */
-        if (!TerminateProcess(proc, sig)) {
+        if (sig != 0 && !TerminateProcess(proc, sig)) {
             errno = ESRCH;
             return -1;
         }