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Re: [libvirt] [PATCH] xen: Use internal interfaces in xenDomainUsedCpus



On 05.08.2013 19:52, Jim Fehlig wrote:
> 
> libvirt typically uses a '*Internal' naming pattern for these types of
> internal functions, e.g. xenUnifiedDomainGetVcpusFlagsInternal.  Also as
> we touch this code we should strive to use the libvirt pattern of
> putting each parameter after the first on a new line when the list of
> parameters exceeds 80 columns.  Finally, since you added a line after
> the xenUnifiedNodeGetInfo declaration, we should add one here too.
> 
Ok, changed.

> 
> I don't think this comment is necessary.  Instead, just send a follow-up
> patch :).

Oh well, it was a kind of reminder, but beside of the "doing it correct" part,
the current usage is ok as there is no special checking between public and
private usage which could lock up... :)

>> @@ -1501,7 +1533,7 @@ xenUnifiedDomainGetXMLDesc(virDomainPtr dom, unsigned int flags)
>>      } else {
>>          char *cpus;
>>          xenUnifiedLock(priv);
>> -        cpus = xenDomainUsedCpus(dom);
>> +        cpus = xenDomainUsedCpus(dom, def);
>>   
> 
> This should be minidef right?  Otherwise def is NULL, resulting in a
> segfault further down the call chain.
>

Absolutely right. I missed to do that in the version I forward ported to HEAD
since I did the fix and testing in an older version. :/
Good you spotted that.

Ok, I updated the patch as suggested (attached).

-Stefan

From 47ce666f6a4d91832883341c56f0a55181698e76 Mon Sep 17 00:00:00 2001
From: Stefan Bader <stefan bader canonical com>
Date: Mon, 15 Jul 2013 16:03:58 +0200
Subject: [PATCH] xen: Use internal interfaces in xenDomainUsedCpus

Since commit 95e18efd most public interfaces (xenUnified...) obtain
a virDomainDefPtr via xenGetDomainDefFor...() which take the unified
lock.
This is already taken before calling xenDomainUsedCpus(), so we get
a deadlock for active guests. Avoid this by splitting up
xenUnifiedDomainGetVcpusFlags() and xenUnifiedDomainGetVcpus() into
public and private function calls (which get the virDomainDefPtr passed)
and use those in xenDomainUsedCpus().

    xenDomainUsedCpus
      ...
      nb_vcpu = xenUnifiedDomainGetMaxVcpus(dom);
        return xenUnifiedDomainGetVcpusFlags(...)
          ...
          if (!(def = xenGetDomainDefForDom(dom)))
            return xenGetDomainDefForUUID(dom->conn, dom->uuid);
              ...
              ret = xenHypervisorLookupDomainByUUID(conn, uuid);
                ...
                xenUnifiedLock(priv);
                name = xenStoreDomainGetName(conn, id);
                xenUnifiedUnlock(priv);
      ...
      if ((ncpus = xenUnifiedDomainGetVcpus(dom, cpuinfo, nb_vcpu,
        ...
        if (!(def = xenGetDomainDefForDom(dom)))
          [again like above]

Signed-off-by: Stefan Bader <stefan bader canonical com>
---
 src/xen/xen_driver.c | 100 +++++++++++++++++++++++++++++++++++----------------
 src/xen/xen_driver.h |   2 +-
 2 files changed, 70 insertions(+), 32 deletions(-)

diff --git a/src/xen/xen_driver.c b/src/xen/xen_driver.c
index 4ae38d3..e1fcbcc 100644
--- a/src/xen/xen_driver.c
+++ b/src/xen/xen_driver.c
@@ -73,12 +73,18 @@
 
 static int
 xenUnifiedNodeGetInfo(virConnectPtr conn, virNodeInfoPtr info);
+
 static int
-xenUnifiedDomainGetMaxVcpus(virDomainPtr dom);
+xenUnifiedDomainGetVcpusFlagsInternal(virDomainPtr dom,
+                                      virDomainDefPtr def,
+                                      unsigned int flags);
 static int
-xenUnifiedDomainGetVcpus(virDomainPtr dom,
-                         virVcpuInfoPtr info, int maxinfo,
-                         unsigned char *cpumaps, int maplen);
+xenUnifiedDomainGetVcpusInternal(virDomainPtr dom,
+                                 virDomainDefPtr def,
+                                 virVcpuInfoPtr info,
+                                 int maxinfo,
+                                 unsigned char *cpumaps,
+                                 int maplen);
 
 
 static bool is_privileged = false;
@@ -173,6 +179,7 @@ xenNumaInit(virConnectPtr conn) {
 /**
  * xenDomainUsedCpus:
  * @dom: the domain
+ * @def: the domain definition
  *
  * Analyze which set of CPUs are used by the domain and
  * return a string providing the ranges.
@@ -181,7 +188,7 @@ xenNumaInit(virConnectPtr conn) {
  *         NULL if the domain uses all CPU or in case of error.
  */
 char *
-xenDomainUsedCpus(virDomainPtr dom)
+xenDomainUsedCpus(virDomainPtr dom, virDomainDefPtr def)
 {
     char *res = NULL;
     int ncpus;
@@ -202,7 +209,9 @@ xenDomainUsedCpus(virDomainPtr dom)
 
     if (priv->nbNodeCpus <= 0)
         return NULL;
-    nb_vcpu = xenUnifiedDomainGetMaxVcpus(dom);
+    nb_vcpu = xenUnifiedDomainGetVcpusFlagsInternal(dom, def,
+                                                    (VIR_DOMAIN_VCPU_LIVE |
+                                                     VIR_DOMAIN_VCPU_MAXIMUM));
     if (nb_vcpu <= 0)
         return NULL;
     if (xenUnifiedNodeGetInfo(dom->conn, &nodeinfo) < 0)
@@ -217,8 +226,8 @@ xenDomainUsedCpus(virDomainPtr dom)
         VIR_ALLOC_N(cpumap, nb_vcpu * cpumaplen) < 0)
         goto done;
 
-    if ((ncpus = xenUnifiedDomainGetVcpus(dom, cpuinfo, nb_vcpu,
-                                          cpumap, cpumaplen)) >= 0) {
+    if ((ncpus = xenUnifiedDomainGetVcpusInternal(dom, def, cpuinfo, nb_vcpu,
+                                                  cpumap, cpumaplen)) >= 0) {
         for (n = 0; n < ncpus; n++) {
             for (m = 0; m < priv->nbNodeCpus; m++) {
                 bool used;
@@ -1416,54 +1425,62 @@ cleanup:
 }
 
 static int
-xenUnifiedDomainGetVcpus(virDomainPtr dom,
-                         virVcpuInfoPtr info, int maxinfo,
-                         unsigned char *cpumaps, int maplen)
+xenUnifiedDomainGetVcpusInternal(virDomainPtr dom,
+                                 virDomainDefPtr def,
+                                 virVcpuInfoPtr info,
+                                 int maxinfo,
+                                 unsigned char *cpumaps,
+                                 int maplen)
 {
     xenUnifiedPrivatePtr priv = dom->conn->privateData;
-    virDomainDefPtr def = NULL;
     int ret = -1;
 
-    if (!(def = xenGetDomainDefForDom(dom)))
-        goto cleanup;
-
-    if (virDomainGetVcpusEnsureACL(dom->conn, def) < 0)
-        goto cleanup;
-
     if (dom->id < 0) {
         if (priv->xendConfigVersion < XEND_CONFIG_VERSION_3_0_4) {
             virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                            _("Cannot get VCPUs of inactive domain"));
-            goto cleanup;
         } else {
-            ret = xenDaemonDomainGetVcpus(dom->conn, def, info, maxinfo, cpumaps, maplen);
+            ret = xenDaemonDomainGetVcpus(dom->conn, def, info, maxinfo,
+                                          cpumaps, maplen);
         }
     } else {
-        ret = xenHypervisorGetVcpus(dom->conn, def, info, maxinfo, cpumaps, maplen);
+        ret = xenHypervisorGetVcpus(dom->conn, def, info, maxinfo, cpumaps,
+                                    maplen);
     }
 
-cleanup:
-    virDomainDefFree(def);
     return ret;
 }
 
 static int
-xenUnifiedDomainGetVcpusFlags(virDomainPtr dom, unsigned int flags)
+xenUnifiedDomainGetVcpus(virDomainPtr dom,
+                         virVcpuInfoPtr info, int maxinfo,
+                         unsigned char *cpumaps, int maplen)
 {
-    xenUnifiedPrivatePtr priv = dom->conn->privateData;
     virDomainDefPtr def = NULL;
     int ret = -1;
 
-    virCheckFlags(VIR_DOMAIN_VCPU_LIVE |
-                  VIR_DOMAIN_VCPU_CONFIG |
-                  VIR_DOMAIN_VCPU_MAXIMUM, -1);
-
     if (!(def = xenGetDomainDefForDom(dom)))
         goto cleanup;
 
-    if (virDomainGetVcpusFlagsEnsureACL(dom->conn, def) < 0)
+    if (virDomainGetVcpusEnsureACL(dom->conn, def) < 0)
         goto cleanup;
 
+    ret = xenUnifiedDomainGetVcpusInternal(dom, def, info, maxinfo, cpumaps,
+                                           maplen);
+
+cleanup:
+    virDomainDefFree(def);
+    return ret;
+}
+
+static int
+xenUnifiedDomainGetVcpusFlagsInternal(virDomainPtr dom,
+                                      virDomainDefPtr def,
+                                      unsigned int flags)
+{
+    xenUnifiedPrivatePtr priv = dom->conn->privateData;
+    int ret = -1;
+
     if (dom->id < 0) {
         if (priv->xendConfigVersion < XEND_CONFIG_VERSION_3_0_4)
             ret = xenXMDomainGetVcpusFlags(dom->conn, def, flags);
@@ -1476,6 +1493,27 @@ xenUnifiedDomainGetVcpusFlags(virDomainPtr dom, unsigned int flags)
             ret = xenDaemonDomainGetVcpusFlags(dom->conn, def, flags);
     }
 
+   return ret;
+}
+
+static int
+xenUnifiedDomainGetVcpusFlags(virDomainPtr dom, unsigned int flags)
+{
+    virDomainDefPtr def = NULL;
+    int ret = -1;
+
+    virCheckFlags(VIR_DOMAIN_VCPU_LIVE |
+                  VIR_DOMAIN_VCPU_CONFIG |
+                  VIR_DOMAIN_VCPU_MAXIMUM, -1);
+
+    if (!(def = xenGetDomainDefForDom(dom)))
+        goto cleanup;
+
+    if (virDomainGetVcpusFlagsEnsureACL(dom->conn, def) < 0)
+        goto cleanup;
+
+    ret = xenUnifiedDomainGetVcpusFlagsInternal(dom, def, flags);
+
 cleanup:
     virDomainDefFree(def);
     return ret;
@@ -1507,7 +1545,7 @@ xenUnifiedDomainGetXMLDesc(virDomainPtr dom, unsigned int flags)
     } else {
         char *cpus;
         xenUnifiedLock(priv);
-        cpus = xenDomainUsedCpus(dom);
+        cpus = xenDomainUsedCpus(dom, minidef);
         xenUnifiedUnlock(priv);
         def = xenDaemonDomainGetXMLDesc(dom->conn, minidef, cpus);
         VIR_FREE(cpus);
diff --git a/src/xen/xen_driver.h b/src/xen/xen_driver.h
index 3c7a8cd..a363161 100644
--- a/src/xen/xen_driver.h
+++ b/src/xen/xen_driver.h
@@ -187,7 +187,7 @@ struct _xenUnifiedPrivate {
 
 typedef struct _xenUnifiedPrivate *xenUnifiedPrivatePtr;
 
-char *xenDomainUsedCpus(virDomainPtr dom);
+char *xenDomainUsedCpus(virDomainPtr dom, virDomainDefPtr def);
 
 virDomainXMLOptionPtr xenDomainXMLConfInit(void);
 
-- 
1.8.1.2

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