[PATCH] (#2) Workaround to fix race condition around libvirt init

30 Aug 2011

# HG changeset patch
# User Sharad Mishra <snmishra@us.ibm.com>
# Date 1314719316 25200
# Node ID c54aafd0b2c6414f91b96bc30e2f148bb78d5c59
# Parent  277b56b3863b5f81a3faa18aeb7b9951b963b489
(#2) Workaround to fix race condition around libvirt init.

This patch fixes the race condition caused when mutiple
threads try to start VMs at the same time. This patch
also fixes the issue of incorrect mem allocation for
VSSD property - emulator.

#2: included Edurdo's patch for make_space
    took care of coding guidelines.

Signed-off-by: Sharad Mishra <snmishra@us.ibm.com>

diff --git a/libxkutil/misc_util.c b/libxkutil/misc_util.c
--- a/libxkutil/misc_util.c
+++ b/libxkutil/misc_util.c
@@ -28,6 +28,7 @@
 #include <stdbool.h>
 #include <stdarg.h>
 #include <unistd.h>
+#include <pthread.h>
 #include <libvirt/libvirt.h>
 #include <libvirt/virterror.h>
 
@@ -45,6 +46,9 @@
 #include "misc_util.h"
 #include "cs_util.h"
 
+static pthread_mutex_t libvirt_mutex = PTHREAD_MUTEX_INITIALIZER;
+/* libvirt library not initialized */
+static int libvirt_initialized = 0;
 
 #define URI_ENV "HYPURI"
 
@@ -114,11 +118,15 @@
 
         CU_DEBUG("Connecting to libvirt with uri `%s'", uri);
 
+        pthread_mutex_lock(&libvirt_mutex);
+
         if (is_read_only())
                 conn = virConnectOpenReadOnly(uri);
         else
                 conn = virConnectOpen(uri);
 
+        pthread_mutex_unlock(&libvirt_mutex);
+
         if (!conn) {
                 CU_DEBUG("Unable to connect to `%s'", uri);
                 return NULL;
@@ -530,7 +538,19 @@
 
 bool libvirt_cim_init(void)
 {
-        return virInitialize() == 0;
+        int ret = 0;
+
+        /* double-check lock pattern used for performance reasons */
+        if (libvirt_initialized == 0) {
+                pthread_mutex_lock(&libvirt_mutex);
+                if (libvirt_initialized == 0) {
+                        ret = virInitialize();
+                        if (ret == 0)
+                                libvirt_initialized = 1;
+                }
+                pthread_mutex_unlock(&libvirt_mutex);
+        }
+        return (ret == 0);
 }
 
 bool check_refs_pfx_match(const CMPIObjectPath *refa,
diff --git a/src/Virt_VirtualSystemManagementService.c b/src/Virt_VirtualSystemManagementService.c
--- a/src/Virt_VirtualSystemManagementService.c
+++ b/src/Virt_VirtualSystemManagementService.c
@@ -188,6 +188,24 @@
         return 1;
 }
 
+static bool make_space(struct virt_device **list, int cur, int new)
+{
+        struct virt_device *tmp;
+
+        tmp = calloc(cur + new, sizeof(*tmp));
+        if (tmp == NULL)
+                return false;
+
+        if (*list) {
+                memcpy(tmp, *list, sizeof(*tmp) * cur);
+                free(*list);
+        }
+
+        *list = tmp;
+
+        return true;
+}
+
 static bool fv_set_emulator(struct domain *domain,
                             const char *emu)
 {
@@ -198,6 +216,11 @@
         if (emu == NULL)
                 return true;
 
+        if (!make_space(&domain->dev_emu, 0, 1)) {
+                CU_DEBUG("Failed to alloc disk list");
+                return false;
+        }
+
         cleanup_virt_device(domain->dev_emu);
 
         domain->dev_emu->type = CIM_RES_TYPE_EMU;
@@ -1369,24 +1392,6 @@
         return msg;
 }
 
-static bool make_space(struct virt_device **list, int cur, int new)
-{
-        struct virt_device *tmp;
-
-        tmp = calloc(cur + new, sizeof(*tmp));
-        if (tmp == NULL)
-                return false;
-
-        if (*list) {
-                memcpy(tmp, *list, sizeof(*tmp) * cur);
-                free(*list);
-        }
-
-        *list = tmp;
-
-        return true;
-}
-
 static char *add_device_nodup(struct virt_device *dev,
                               struct virt_device *list,
                               int max,

    

Sharad Mishra

Eduardo Lima (Etrunko)

Sharad Mishra

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