[PATCH 11/29] libxl: events: Make libxl__async_exec_* pass caller an rc

[Ian Jackson <ian.jackson@eu.citrix.com>]

The internal user of libxl__async_exec_start et al now gets an rc as
well as the process's exit status.

For now this is always either 0 or ERROR_FAIL, but with ao
cancellation this will possibly be CANCELLED or TIMEDOUT too.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: New patch due to rebause; v1 had changes to device_hotplug_*
     scripts instead.
    Callback now gets unambiguous information about error situation:
     previously, if only thing that went wrong was that child died
     badly, rc would be FAILED, which was unambigously; now rc=0.
    Add a comment document the meaning of the rc and status parameters
     to the callback.
---
 tools/libxl/libxl_aoutils.c         |    9 ++++++---
 tools/libxl/libxl_device.c          |   13 +++++++++----
 tools/libxl/libxl_internal.h        |   11 ++++++++++-
 tools/libxl/libxl_netbuffer.c       |   19 ++++++++++---------
 tools/libxl/libxl_remus_disk_drbd.c |    8 +++++---
 5 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
index 754e2d1..891cdb8 100644
--- a/tools/libxl/libxl_aoutils.c
+++ b/tools/libxl/libxl_aoutils.c
@@ -483,11 +483,12 @@ static void async_exec_done(libxl__egc *egc,
     libxl__ev_time_deregister(gc, &aes->time);
 
     if (status) {
-        libxl_report_child_exitstatus(CTX, LIBXL__LOG_ERROR,
-                                      aes->what, pid, status);
+        if (!aes->rc)
+            libxl_report_child_exitstatus(CTX, LIBXL__LOG_ERROR,
+                                          aes->what, pid, status);
     }
 
-    aes->callback(egc, aes, status);
+    aes->callback(egc, aes, aes->rc, status);
 }
 
 void libxl__async_exec_init(libxl__async_exec_state *aes)
@@ -506,6 +507,8 @@ int libxl__async_exec_start(libxl__async_exec_state *aes)
     libxl__ev_child *const child = &aes->child;
     char ** const args = aes->args;
 
+    aes->rc = 0;
+
     /* Set execution timeout */
     if (libxl__ev_time_register_rel(ao, &aes->time,
                                     async_exec_timeout,
diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index c80749f..84114ff 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -729,7 +729,7 @@ static void device_hotplug(libxl__egc *egc, libxl__ao_device *aodev);
 
 static void device_hotplug_child_death_cb(libxl__egc *egc,
                                           libxl__async_exec_state *aes,
-                                          int status);
+                                          int rc, int status);
 
 static void device_destroy_be_watch_cb(libxl__egc *egc,
                                        libxl__xswait_state *xswait,
@@ -1052,7 +1052,7 @@ out:
 
 static void device_hotplug_child_death_cb(libxl__egc *egc,
                                           libxl__async_exec_state *aes,
-                                          int status)
+                                          int rc, int status)
 {
     libxl__ao_device *aodev = CONTAINER_OF(aes, *aodev, aes);
     STATE_AO_GC(aodev->ao);
@@ -1061,12 +1061,17 @@ static void device_hotplug_child_death_cb(libxl__egc *egc,
 
     device_hotplug_clean(gc, aodev);
 
-    if (status) {
+    if (status && !rc) {
         hotplug_error = libxl__xs_read(gc, XBT_NULL,
                                        GCSPRINTF("%s/hotplug-error", be_path));
         if (hotplug_error)
             LOG(ERROR, "script: %s", hotplug_error);
-        aodev->rc = ERROR_FAIL;
+        rc = ERROR_FAIL;
+    }
+
+    if (rc) {
+        if (!aodev->rc)
+            aodev->rc = rc;
         if (aodev->action == LIBXL__DEVICE_ACTION_ADD)
             /*
              * Only fail on device connection, on disconnection
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index b615fc5..02cac7b 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2089,7 +2089,15 @@ _hidden const char *libxl__run_dir_path(void);
 typedef struct libxl__async_exec_state libxl__async_exec_state;
 
 typedef void libxl__async_exec_callback(libxl__egc *egc,
-                        libxl__async_exec_state *aes, int status);
+                        libxl__async_exec_state *aes, int rc, int status);
+/*
+ * Meaning of status and rc:
+ *  rc==0, status==0    all went well
+ *  rc==0, status!=0    everything OK except child exited nonzero (logged)
+ *  rc!=0               something else went wrong (status is real
+ *                       exit status, maybe reflecting SIGKILL if aes
+ *                       code killed the child).  Logged unless CANCELLED.
+ */
 
 struct libxl__async_exec_state {
     /* caller must fill these in */
@@ -2105,6 +2113,7 @@ struct libxl__async_exec_state {
     /* private */
     libxl__ev_time time;
     libxl__ev_child child;
+    int rc;
 };
 
 void libxl__async_exec_init(libxl__async_exec_state *aes);
diff --git a/tools/libxl/libxl_netbuffer.c b/tools/libxl/libxl_netbuffer.c
index edc6843..ff2d6c7 100644
--- a/tools/libxl/libxl_netbuffer.c
+++ b/tools/libxl/libxl_netbuffer.c
@@ -219,10 +219,10 @@ out:
 
 static void netbuf_setup_script_cb(libxl__egc *egc,
                                    libxl__async_exec_state *aes,
-                                   int status);
+                                   int rc, int status);
 static void netbuf_teardown_script_cb(libxl__egc *egc,
                                       libxl__async_exec_state *aes,
-                                      int status);
+                                      int rc, int status);
 
 /*
  * the script needs the following env & args
@@ -327,14 +327,13 @@ out:
  */
 static void netbuf_setup_script_cb(libxl__egc *egc,
                                    libxl__async_exec_state *aes,
-                                   int status)
+                                   int rc, int status)
 {
     libxl__ao_device *aodev = CONTAINER_OF(aes, *aodev, aes);
     libxl__remus_device *dev = CONTAINER_OF(aodev, *dev, aodev);
     libxl__remus_device_nic *remus_nic = dev->concrete_data;
     libxl__remus_devices_state *rds = dev->rds;
     const char *out_path_base, *hotplug_error = NULL;
-    int rc;
 
     STATE_AO_GC(rds->ao);
 
@@ -344,6 +343,11 @@ static void netbuf_setup_script_cb(libxl__egc *egc,
     const char *const vif = remus_nic->vif;
     const char **const ifb = &remus_nic->ifb;
 
+    if (status && !rc)
+        rc = ERROR_FAIL;
+    if (rc)
+        goto out;
+
     /*
      * we need to get ifb first because it's needed for teardown
      */
@@ -411,17 +415,14 @@ out:
 
 static void netbuf_teardown_script_cb(libxl__egc *egc,
                                       libxl__async_exec_state *aes,
-                                      int status)
+                                      int rc, int status)
 {
-    int rc;
     libxl__ao_device *aodev = CONTAINER_OF(aes, *aodev, aes);
     libxl__remus_device *dev = CONTAINER_OF(aodev, *dev, aodev);
     libxl__remus_device_nic *remus_nic = dev->concrete_data;
 
-    if (status)
+    if (status && !rc)
         rc = ERROR_FAIL;
-    else
-        rc = 0;
 
     free_qdisc(remus_nic);
 
diff --git a/tools/libxl/libxl_remus_disk_drbd.c b/tools/libxl/libxl_remus_disk_drbd.c
index 5e0c9a6..fc76b89 100644
--- a/tools/libxl/libxl_remus_disk_drbd.c
+++ b/tools/libxl/libxl_remus_disk_drbd.c
@@ -78,7 +78,7 @@ out:
 /* callbacks */
 static void match_async_exec_cb(libxl__egc *egc,
                                 libxl__async_exec_state *aes,
-                                int status);
+                                int rc, int status);
 
 /* implementations */
 
@@ -133,9 +133,8 @@ out:
 
 static void match_async_exec_cb(libxl__egc *egc,
                                 libxl__async_exec_state *aes,
-                                int status)
+                                int rc, int status)
 {
-    int rc;
     libxl__ao_device *aodev = CONTAINER_OF(aes, *aodev, aes);
     libxl__remus_device *dev = CONTAINER_OF(aodev, *dev, aodev);
     libxl__remus_drbd_disk *drbd_disk;
@@ -143,6 +142,9 @@ static void match_async_exec_cb(libxl__egc *egc,
 
     STATE_AO_GC(aodev->ao);
 
+    if (rc)
+        goto out;
+
     if (status) {
         rc = ERROR_REMUS_DEVOPS_DOES_NOT_MATCH;
         /* BUG: seems to assume that any exit status means `no match' */
-- 
1.7.10.4