[PATCH 3 of 9] libxl: signal caller if domain already destroyed on domain death event

[Ian Campbell <ian.campbell@citrix.com>]

# HG changeset patch
# User Ian Campbell <ian.campbell@citrix.com>
# Date 1280140562 -3600
# Node ID 1e0b63948031587b958ea307410d19c7b2be9614
# Parent  f6300d42a667cf6a1a02fc065ecd9eaea0e10ecc
libxl: signal caller if domain already destroyed on domain death event

Currently libxl_event_get_domain_death_info returns 0 if the event was
not a domain death event and 1 if it was but does not infom the user
if someone else has already cleaned up the domain, which means the
caller must replicate some of the logic from within libxl.

Instead have the libxl_event_get_XXX_info functions required that the
event is of the right type (the caller must have recently switched on
event->type anyway).

This allows the return codes to be used in an event specific way and
we take advantage of this by returning an error from
libxl_event_get_domain_death_info if the domain is not dying.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>

diff -r f6300d42a667 -r 1e0b63948031 tools/libxl/libxl.c
--- a/tools/libxl/libxl.c	Mon Jul 26 11:36:02 2010 +0100
+++ b/tools/libxl/libxl.c	Mon Jul 26 11:36:02 2010 +0100
@@ -721,54 +721,54 @@ int libxl_free_waiter(libxl_waiter *wait
     return 0;
 }
 
+/*
+ * Returns:
+ *  - 0 if the domain is dead and there is no cleanup to be done. e.g because someone else has already done it.
+ *  - 1 if the domain is dead and there is cleanup to be done.
+ *
+ * Can return error if the domain exists and is still running
+ */
 int libxl_event_get_domain_death_info(struct libxl_ctx *ctx, uint32_t domid, libxl_event *event, struct libxl_dominfo *info)
 {
-    int rc = 0, ret;
-    if (event && event->type == LIBXL_EVENT_DOMAIN_DEATH) {
-        ret = libxl_domain_info(ctx, info, domid);
+    if (libxl_domain_info(ctx, info, domid) < 0)
+        return 0;
 
-        if (ret == 0 && info->domid == domid) {
-            if (info->running || (!info->shutdown && !info->dying && !info->crashed))
-                    goto out;
-                rc = 1;
-                goto out;
-        }
-        memset(info, 0, sizeof(*info));
-        rc = 1;
-        goto out;
-    }
-out:
-    return rc;
+    if (info->running || (!info->shutdown && !info->dying && !info->crashed))
+        return ERROR_INVAL;
+
+    return 1;
 }
 
+/*
+ * Returns true and fills *disk if the caller should eject the disk
+ */
 int libxl_event_get_disk_eject_info(struct libxl_ctx *ctx, uint32_t domid, libxl_event *event, libxl_device_disk *disk)
 {
-    if (event && event->type == LIBXL_EVENT_DISK_EJECT) {
-        char *path;
-        char *backend;
-        char *value = libxl_xs_read(ctx, XBT_NULL, event->path);
+    char *path;
+    char *backend;
+    char *value;
 
-        if (!value || strcmp(value,  "eject"))
-            return 0;
+    value = libxl_xs_read(ctx, XBT_NULL, event->path);
 
-        path = strdup(event->path);
-        path[strlen(path) - 6] = '\0';
-        backend = libxl_xs_read(ctx, XBT_NULL, libxl_sprintf(ctx, "%s/backend", path));
+    if (!value || strcmp(value,  "eject"))
+        return 0;
 
-        disk->backend_domid = 0;
-        disk->domid = domid;
-        disk->physpath = NULL;
-        disk->phystype = 0;
-        /* this value is returned to the user: do not free right away */
-        disk->virtpath = libxl_xs_read(ctx, XBT_NULL, libxl_sprintf(ctx, "%s/dev", backend));
-        disk->unpluggable = 1;
-        disk->readwrite = 0;
-        disk->is_cdrom = 1;
+    path = strdup(event->path);
+    path[strlen(path) - 6] = '\0';
+    backend = libxl_xs_read(ctx, XBT_NULL, libxl_sprintf(ctx, "%s/backend", path));
 
-        free(path);
-        return 1;
-    }
-    return 0;
+    disk->backend_domid = 0;
+    disk->domid = domid;
+    disk->physpath = NULL;
+    disk->phystype = 0;
+    /* this value is returned to the user: do not free right away */
+    disk->virtpath = libxl_xs_read(ctx, XBT_NULL, libxl_sprintf(ctx, "%s/dev", backend));
+    disk->unpluggable = 1;
+    disk->readwrite = 0;
+    disk->is_cdrom = 1;
+
+    free(path);
+    return 1;
 }
 
 static int libxl_destroy_device_model(struct libxl_ctx *ctx, uint32_t domid)
diff -r f6300d42a667 -r 1e0b63948031 tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c	Mon Jul 26 11:36:02 2010 +0100
+++ b/tools/libxl/xl_cmdimpl.c	Mon Jul 26 11:36:02 2010 +0100
@@ -1338,7 +1338,6 @@ start:
         struct libxl_dominfo info;
         libxl_event event;
         libxl_device_disk disk;
-        memset(&info, 0x00, sizeof(xc_domaininfo_t));
 
         FD_ZERO(&rfds);
         FD_SET(fd, &rfds);
@@ -1349,12 +1348,17 @@ start:
         libxl_get_event(&ctx, &event);
         switch (event.type) {
             case LIBXL_EVENT_DOMAIN_DEATH:
-                if (libxl_event_get_domain_death_info(&ctx, domid, &event, &info)) {
-                    LOG("Domain %d is dead", domid);
-                    if (info.crashed || info.dying || (info.shutdown && info.shutdown_reason != SHUTDOWN_suspend)) {
+                ret = libxl_event_get_domain_death_info(&ctx, domid, &event, &info);
+
+                if (ret < 0) continue;
+
+                LOG("Domain %d is dead", domid);
+
+                if (ret) {
+                    if (info.shutdown_reason != SHUTDOWN_suspend) {
                         LOG("Domain %d needs to be clean: destroying the domain", domid);
                         libxl_domain_destroy(&ctx, domid, 0);
-                        if (info.shutdown && info.shutdown_reason == SHUTDOWN_reboot) {
+                        if (info.shutdown_reason == SHUTDOWN_reboot) {
                             libxl_free_waiter(w1);
                             libxl_free_waiter(w2);
                             free(w1);