libxl: Refactor kill_device_model to libxl__kill_xs_path

Move kill_device_model to libxl__kill_xs_path so we have a helper to
kill a process from a pid stored in xenstore.  We'll be using it to kill
vchan-qmp-proxy.

libxl__kill_xs_path takes a "what" string for use in printing error
messages.  kill_device_model is retained in libxl_dm.c to provide the
string.

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/libxl/libxl_aoutils.c

@@ -626,6 +626,38 @@ void libxl__kill(libxl__gc *gc, pid_t pid, int sig, const char *what)
                 what, (unsigned long)pid, sig);
 }
 
+/* Generic function to signal (HUP) a pid stored in xenstore */
+int libxl__kill_xs_path(libxl__gc *gc, const char *xs_path_pid,
+                        const char *what)
+{
+    const char *xs_pid;
+    int ret, pid;
+
+    ret = libxl__xs_read_checked(gc, XBT_NULL, xs_path_pid, &xs_pid);
+    if (ret || !xs_pid) {
+        LOG(ERROR, "unable to find %s pid in %s", what, xs_path_pid);
+        ret = ret ? : ERROR_FAIL;
+        goto out;
+    }
+    pid = atoi(xs_pid);
+
+    ret = kill(pid, SIGHUP);
+    if (ret < 0 && errno == ESRCH) {
+        LOG(ERROR, "%s already exited", what);
+        ret = 0;
+    } else if (ret == 0) {
+        LOG(DEBUG, "%s signaled", what);
+        ret = 0;
+    } else {
+        LOGE(ERROR, "failed to kill %s [%d]", what, pid);
+        ret = ERROR_FAIL;
+        goto out;
+    }
+
+out:
+    return ret;
+}
+
 /*
  * Local variables:
  * mode: C

tools/libxl/libxl_dm.c

@@ -3225,32 +3225,7 @@ out:
 /* Generic function to signal a Qemu instance to exit */
 static int kill_device_model(libxl__gc *gc, const char *xs_path_pid)
 {
-    const char *xs_pid;
-    int ret, pid;
-
-    ret = libxl__xs_read_checked(gc, XBT_NULL, xs_path_pid, &xs_pid);
-    if (ret || !xs_pid) {
-        LOG(ERROR, "unable to find device model pid in %s", xs_path_pid);
-        ret = ret ? : ERROR_FAIL;
-        goto out;
-    }
-    pid = atoi(xs_pid);
-
-    ret = kill(pid, SIGHUP);
-    if (ret < 0 && errno == ESRCH) {
-        LOG(ERROR, "Device Model already exited");
-        ret = 0;
-    } else if (ret == 0) {
-        LOG(DEBUG, "Device Model signaled");
-        ret = 0;
-    } else {
-        LOGE(ERROR, "failed to kill Device Model [%d]", pid);
-        ret = ERROR_FAIL;
-        goto out;
-    }
-
-out:
-    return ret;
+    return libxl__kill_xs_path(gc, xs_path_pid, "Device Model");
 }
 
 /* Helper to destroy a Qdisk backend */

tools/libxl/libxl_internal.h

@@ -2711,6 +2711,9 @@ int libxl__async_exec_start(libxl__async_exec_state *aes);
 bool libxl__async_exec_inuse(const libxl__async_exec_state *aes);
 
 _hidden void libxl__kill(libxl__gc *gc, pid_t pid, int sig, const char *what);
+/* kill SIGHUP a pid stored in xenstore */
+_hidden int libxl__kill_xs_path(libxl__gc *gc, const char *xs_path_pid,
+                                const char *what);
 
 /*----- device addition/removal -----*/