[Xen-changelog] [xen-unstable] libxl: signal caller if domain already destroyed on domain death event

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1280246331 -3600
# Node ID c7af12b752ca9c445d1c69a52de94db0cf7b8dc8
# Parent  5d8db087cc453e8758216bcd8b5da710282990d4
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@xxxxxxxxxx>
Committed-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 tools/libxl/libxl.c      |   74 ++++++++++++++++++++---------------------------
 tools/libxl/libxl.h      |   17 ++++++++++
 tools/libxl/xl_cmdimpl.c |   14 +++++---
 3 files changed, 58 insertions(+), 47 deletions(-)

diff -r 5d8db087cc45 -r c7af12b752ca tools/libxl/libxl.c
--- a/tools/libxl/libxl.c       Tue Jul 27 16:58:26 2010 +0100
+++ b/tools/libxl/libxl.c       Tue Jul 27 16:58:51 2010 +0100
@@ -704,52 +704,42 @@ int libxl_free_waiter(libxl_waiter *wait
 
 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 (ret == 0 && info->domid == domid) {
-            if (info->running || (!info->shutdown && !info->dying))
-                    goto out;
-                rc = 1;
-                goto out;
-        }
-        memset(info, 0, sizeof(*info));
-        rc = 1;
-        goto out;
-    }
-out:
-    return rc;
+    if (libxl_domain_info(ctx, info, domid) < 0)
+        return 0;
+
+    if (info->running || (!info->shutdown && !info->dying))
+        return ERROR_INVAL;
+
+    return 1;
 }
 
 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);
-
-        if (!value || strcmp(value,  "eject"))
-            return 0;
-
-        path = strdup(event->path);
-        path[strlen(path) - 6] = '\0';
-        backend = libxl_xs_read(ctx, XBT_NULL, libxl_sprintf(ctx, 
"%s/backend", path));
-
-        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;
-    }
-    return 0;
+    char *path;
+    char *backend;
+    char *value;
+
+    value = libxl_xs_read(ctx, XBT_NULL, event->path);
+
+    if (!value || strcmp(value,  "eject"))
+        return 0;
+
+    path = strdup(event->path);
+    path[strlen(path) - 6] = '\0';
+    backend = libxl_xs_read(ctx, XBT_NULL, libxl_sprintf(ctx, "%s/backend", 
path));
+
+    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 5d8db087cc45 -r c7af12b752ca tools/libxl/libxl.h
--- a/tools/libxl/libxl.h       Tue Jul 27 16:58:26 2010 +0100
+++ b/tools/libxl/libxl.h       Tue Jul 27 16:58:51 2010 +0100
@@ -393,7 +393,24 @@ int libxl_free_event(libxl_event *event)
 int libxl_free_event(libxl_event *event);
 int libxl_free_waiter(libxl_waiter *waiter);
 
+/*
+ * Returns:
+ *  - 0 if the domain is dead but 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.
+ *
+ * *info will contain valid domain state iff 1 is returned. In
+ * particular if 1 is returned then info->shutdown_reason is
+ * guaranteed to be valid since by definition the domain is
+ * (shutdown||dying))
+ */
 int libxl_event_get_domain_death_info(struct libxl_ctx *ctx, uint32_t domid, 
libxl_event *event, struct libxl_dominfo *info);
+
+/*
+ * 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);
 
 int libxl_domain_rename(struct libxl_ctx *ctx, uint32_t domid,
diff -r 5d8db087cc45 -r c7af12b752ca tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c  Tue Jul 27 16:58:26 2010 +0100
+++ b/tools/libxl/xl_cmdimpl.c  Tue Jul 27 16:58:51 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.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);

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