Rewrite virAtomic APIs using GLib's atomic ops code

There are a few issues with the current virAtomic APIs

 - They require use of a virAtomicInt struct instead of a plain
   int type
 - Several of the methods do not implement memory barriers
 - The methods do not implement compiler re-ordering barriers
 - There is no Win32 native impl

The GLib library has a nice LGPLv2+ licensed impl of atomic
ops that works with GCC, Win32, or pthreads.h that addresses
all these problems. The main downside to their code is that
the pthreads impl uses a single global mutex, instead of
a per-variable mutex. Given that it does have a Win32 impl
though, we don't expect anyone to seriously use the pthread.h
impl, so this downside is not significant.

* .gitignore: Ignore test case
* configure.ac: Check for which atomic ops impl to use
* src/Makefile.am: Add viratomic.c
* src/nwfilter/nwfilter_dhcpsnoop.c: Switch to new atomic
  ops APIs and plain int datatype
* src/util/viratomic.h: inline impls of all atomic ops
  for GCC, Win32 and pthreads
* src/util/viratomic.c: Global pthreads mutex for atomic
  ops
* tests/viratomictest.c: Test validate to validate safety
  of atomic ops.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

.gitignore

@@ -152,6 +152,7 @@
 /tests/statstest
 /tests/storagebackendsheepdogtest
 /tests/utiltest
+/tests/viratomictest
 /tests/virauthconfigtest
 /tests/virbuftest
 /tests/virdrivermoduletest

configure.ac

@@ -159,6 +159,63 @@ AC_CHECK_HEADERS([pwd.h paths.h regex.h sys/un.h \
   sys/un.h sys/syscall.h netinet/tcp.h ifaddrs.h libtasn1.h \
   net/if.h execinfo.h])
 
+dnl We need to decide at configure time if libvirt will use real atomic
+dnl operations ("lock free") or emulated ones with a mutex.
+
+dnl Note that the atomic ops are only available with GCC on x86 when
+dnl using -march=i486 or higher.  If we detect that the atomic ops are
+dnl not available but would be available given the right flags, we want
+dnl to abort and advise the user to fix their CFLAGS.  It's better to do
+dnl that then to silently fall back on emulated atomic ops just because
+dnl the user had the wrong build environment.
+
+atomic_ops=
+
+AC_MSG_CHECKING([for atomic ops implementation])
+
+AC_TRY_COMPILE([], [__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4;],[
+  atomic_ops=gcc
+],[])
+
+if test "$atomic_ops" = "" ; then
+  SAVE_CFLAGS="${CFLAGS}"
+  CFLAGS="-march=i486"
+  AC_TRY_COMPILE([],
+                 [__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4;],
+                 [AC_MSG_ERROR([Libvirt must be built with -march=i486 or later.])],
+                 [])
+  CFLAGS="${SAVE_CFLAGS}"
+
+  case "$host" in
+    *-*-mingw* | *-*-msvc* )
+      atomic_ops=win32
+      ;;
+    *)
+      if test "$ac_cv_header_pthread_h" = "yes" ; then
+        atomic_ops=pthread
+      else
+        AC_MSG_ERROR([Libvirt must be built with GCC or have pthread.h on non-Win32 platforms])
+      fi
+      ;;
+  esac
+fi
+
+case "$atomic_ops" in
+   gcc)
+     AC_DEFINE([VIR_ATOMIC_OPS_GCC],[1],[Use GCC atomic ops])
+     ;;
+   win32)
+     AC_DEFINE([VIR_ATOMIC_OPS_WIN32],[1],[Use Win32 atomic ops])
+     ;;
+   pthread)
+     AC_DEFINE([VIR_ATOMIC_OPS_PTHREAD],[1],[Use pthread atomic ops emulation])
+     ;;
+esac
+AM_CONDITIONAL([WITH_ATOMIC_OPS_PTHREAD],[test "$atomic_ops" = "pthread"])
+AC_MSG_RESULT([$atomic_ops])
+
+
+
 AC_MSG_CHECKING([for struct ifreq in net/if.h])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
    [[

src/Makefile.am

@@ -79,7 +79,7 @@ UTIL_SOURCES =							\
 		util/threadpool.c util/threadpool.h		\
 		util/uuid.c util/uuid.h				\
 		util/util.c util/util.h				\
-		util/viratomic.h				\
+		util/viratomic.h util/viratomic.c		\
 		util/viraudit.c util/viraudit.h			\
 		util/virauth.c util/virauth.h			\
 		util/virauthconfig.c util/virauthconfig.h	\
@@ -1317,9 +1317,14 @@ if HAVE_SASL
 USED_SYM_FILES += libvirt_sasl.syms
 endif
 
+if WITH_ATOMIC_OPS_PTHREAD
+USED_SYM_FILES += libvirt_atomic.syms
+endif
+
 EXTRA_DIST += \
   libvirt_public.syms		\
   libvirt_private.syms		\
+  libvirt_atomic.syms		\
   libvirt_driver_modules.syms	\
   libvirt_daemon.syms		\
   libvirt_linux.syms		\

src/libvirt_atomic.syms

@@ -0,0 +1,3 @@
+
+# viratomic.h
+virAtomicLock;

src/nwfilter/nwfilter_dhcpsnoop.c

@@ -78,9 +78,9 @@
 struct virNWFilterSnoopState {
     /* lease file */
     int                  leaseFD;
-    virAtomicInt         nLeases; /* number of active leases */
+    int                  nLeases; /* number of active leases */
-    virAtomicInt         wLeases; /* number of written leases */
+    int                  wLeases; /* number of written leases */
-    virAtomicInt         nThreads; /* number of running threads */
+    int                  nThreads; /* number of running threads */
     /* thread management */
     virHashTablePtr      snoopReqs;
     virHashTablePtr      ifnameToKey;
@@ -126,7 +126,7 @@ struct _virNWFilterSnoopReq {
      * publicSnoopReqs hash, the refctr may only
      * be modified with the SnoopLock held
      */
-    virAtomicInt                         refctr;
+    int                                  refctr;
 
     virNWFilterTechDriverPtr             techdriver;
     char                                *ifname;
@@ -240,7 +240,7 @@ struct _virNWFilterDHCPDecodeJob {
     unsigned char packet[PCAP_PBUFSIZE];
     int caplen;
     bool fromVM;
-    virAtomicIntPtr qCtr;
+    int *qCtr;
 };
 
 # define DHCP_PKT_RATE          10 /* pkts/sec */
@@ -271,7 +271,7 @@ struct _virNWFilterSnoopPcapConf {
     const pcap_direction_t dir;
     const char *filter;
     virNWFilterSnoopRateLimitConf rateLimit; /* indep. rate limiters */
-    virAtomicInt qCtr; /* number of jobs in the worker's queue */
+    int qCtr; /* number of jobs in the worker's queue */
     const unsigned int maxQSize;
     unsigned long long penaltyTimeoutAbs;
 };
@@ -588,8 +588,7 @@ virNWFilterSnoopReqNew(const char *ifkey)
 
     req->threadStatus = THREAD_STATUS_NONE;
 
-    if (virAtomicIntInit(&req->refctr) < 0 ||
+    if (virStrcpyStatic(req->ifkey, ifkey) == NULL ||
-        virStrcpyStatic(req->ifkey, ifkey) == NULL ||
         virMutexInitRecursive(&req->lock) < 0)
         goto err_free_req;
 
@@ -622,7 +621,7 @@ virNWFilterSnoopReqFree(virNWFilterSnoopReqPtr req)
     if (!req)
         return;
 
-    if (virAtomicIntRead(&req->refctr) != 0)
+    if (virAtomicIntGet(&req->refctr) != 0)
         return;
 
     /* free all leases */
@@ -715,7 +714,7 @@ virNWFilterSnoopReqPut(virNWFilterSnoopReqPtr req)
 
     virNWFilterSnoopLock();
 
-    if (virAtomicIntDec(&req->refctr) == 0) {
+    if (virAtomicIntDecAndTest(&req->refctr)) {
         /*
          * delete the request:
          * - if we don't find req on the global list anymore
@@ -897,7 +896,7 @@ virNWFilterSnoopReqLeaseDel(virNWFilterSnoopReqPtr req,
 skip_instantiate:
     VIR_FREE(ipl);
 
-    virAtomicIntDec(&virNWFilterSnoopState.nLeases);
+    virAtomicIntDecAndTest(&virNWFilterSnoopState.nLeases);
 
 lease_not_found:
     VIR_FREE(ipstr);
@@ -1159,7 +1158,7 @@ static void virNWFilterDHCPDecodeWorker(void *jobdata, void *opaque)
                        _("Instantiation of rules failed on "
                          "interface '%s'"), req->ifname);
     }
-    virAtomicIntDec(job->qCtr);
+    virAtomicIntDecAndTest(job->qCtr);
     VIR_FREE(job);
 }
 
@@ -1170,7 +1169,7 @@ static int
 virNWFilterSnoopDHCPDecodeJobSubmit(virThreadPoolPtr pool,
                                     virNWFilterSnoopEthHdrPtr pep,
                                     int len, pcap_direction_t dir,
-                                    virAtomicIntPtr qCtr)
+                                    int *qCtr)
 {
     virNWFilterDHCPDecodeJobPtr job;
     int ret;
@@ -1376,8 +1375,7 @@ virNWFilterDHCPSnoopThread(void *req0)
                 virNWFilterSnoopDHCPOpen(req->ifname, &req->macaddr,
                                          pcapConf[i].filter,
                                          pcapConf[i].dir);
-            if (!pcapConf[i].handle ||
+            if (!pcapConf[i].handle) {
-                virAtomicIntInit(&pcapConf[i].qCtr) < 0) {
                 error = true;
                 break;
             }
@@ -1488,7 +1486,7 @@ virNWFilterDHCPSnoopThread(void *req0)
                 unsigned int diff;
 
                 /* submit packet to worker thread */
-                if (virAtomicIntRead(&pcapConf[i].qCtr) >
+                if (virAtomicIntGet(&pcapConf[i].qCtr) >
                     pcapConf[i].maxQSize) {
                     if (last_displayed_queue - time(0) > 10) {
                         last_displayed_queue = time(0);
@@ -1554,7 +1552,7 @@ exit:
             pcap_close(pcapConf[i].handle);
     }
 
-    virAtomicIntDec(&virNWFilterSnoopState.nThreads);
+    virAtomicIntDecAndTest(&virNWFilterSnoopState.nThreads);
 
     return;
 }
@@ -1805,7 +1803,7 @@ virNWFilterSnoopLeaseFileSave(virNWFilterSnoopIPLeasePtr ipl)
 
     /* keep dead leases at < ~95% of file size */
     if (virAtomicIntInc(&virNWFilterSnoopState.wLeases) >=
-        virAtomicIntRead(&virNWFilterSnoopState.nLeases) * 20)
+        virAtomicIntGet(&virNWFilterSnoopState.nLeases) * 20)
         virNWFilterSnoopLeaseFileLoad();   /* load & refresh lease file */
 
 err_exit:
@@ -1836,7 +1834,7 @@ virNWFilterSnoopPruneIter(const void *payload,
     /*
      * have the entry removed if it has no leases and no one holds a ref
      */
-    del_req = ((req->start == NULL) && (virAtomicIntRead(&req->refctr) == 0));
+    del_req = ((req->start == NULL) && (virAtomicIntGet(&req->refctr) == 0));
 
     virNWFilterSnoopReqUnlock(req);
 
@@ -1994,9 +1992,9 @@ virNWFilterSnoopLeaseFileLoad(void)
 static void
 virNWFilterSnoopJoinThreads(void)
 {
-    while (virAtomicIntRead(&virNWFilterSnoopState.nThreads) != 0) {
+    while (virAtomicIntGet(&virNWFilterSnoopState.nThreads) != 0) {
         VIR_WARN("Waiting for snooping threads to terminate: %u\n",
-                 virAtomicIntRead(&virNWFilterSnoopState.nThreads));
+                 virAtomicIntGet(&virNWFilterSnoopState.nThreads));
         usleep(1000 * 1000);
     }
 }
@@ -2061,10 +2059,7 @@ virNWFilterDHCPSnoopInit(void)
     VIR_DEBUG("Initializing DHCP snooping");
 
     if (virMutexInitRecursive(&virNWFilterSnoopState.snoopLock) < 0 ||
-        virMutexInit(&virNWFilterSnoopState.activeLock) < 0 ||
+        virMutexInit(&virNWFilterSnoopState.activeLock) < 0)
-        virAtomicIntInit(&virNWFilterSnoopState.nLeases) < 0 ||
-        virAtomicIntInit(&virNWFilterSnoopState.wLeases) < 0 ||
-        virAtomicIntInit(&virNWFilterSnoopState.nThreads) < 0)
         return -1;
 
     virNWFilterSnoopState.ifnameToKey = virHashCreate(0, NULL);

src/util/viratomic.c

@@ -0,0 +1,35 @@
+/*
+ * viratomic.h: atomic integer operations
+ *
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * Based on code taken from GLib 2.32, under the LGPLv2+
+ *
+ * Copyright (C) 2011 Ryan Lortie
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library;  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <config.h>
+
+#include "viratomic.h"
+
+
+#ifdef VIR_ATOMIC_OPS_PTHREAD
+
+pthread_mutex_t virAtomicLock = PTHREAD_MUTEX_INITIALIZER;
+
+#endif

src/util/viratomic.h

@@ -1,10 +1,11 @@
 /*
  * viratomic.h: atomic integer operations
  *
- * Copyright (C) 2012 IBM Corporation
+ * Copyright (C) 2012 Red Hat, Inc.
  *
- * Authors:
+ * Based on code taken from GLib 2.32, under the LGPLv2+
- *     Stefan Berger <stefanb@linux.vnet.ibm.com>
+ *
+ * Copyright (C) 2011 Ryan Lortie
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -25,130 +26,422 @@
 #ifndef __VIR_ATOMIC_H__
 # define __VIR_ATOMIC_H__
 
-# include "threads.h"
+# include "internal.h"
 
-typedef struct _virAtomicInt virAtomicInt;
+/**
-typedef virAtomicInt *virAtomicIntPtr;
+ * virAtomicIntGet:
+ * Gets the current value of atomic.
+ *
+ * This call acts as a full compiler and hardware memory barrier
+ * (before the get)
+ */
+int virAtomicIntGet(volatile int *atomic)
+    ATTRIBUTE_NONNULL(1);
 
-# define __VIR_ATOMIC_USES_LOCK
+/**
+ * virAtomicIntSet:
+ * Sets the value of atomic to newval.
+ *
+ * This call acts as a full compiler and hardware memory barrier
+ * (after the set)
+ */
+void virAtomicIntSet(volatile int *atomic,
+                     int newval)
+    ATTRIBUTE_NONNULL(1);
 
-# if ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 1)) || (__GNUC__ > 4)
+/**
-#  undef __VIR_ATOMIC_USES_LOCK
+ * virAtomicIntInc:
+ * Increments the value of atomic by 1.
+ *
+ * Think of this operation as an atomic version of
+ * { *atomic += 1; return *atomic; }
+ *
+ * This call acts as a full compiler and hardware memory barrier.
+ */
+int virAtomicIntInc(volatile int *atomic)
+    ATTRIBUTE_NONNULL(1);
+
+/**
+ * virAtomicIntDecAndTest:
+ * Decrements the value of atomic by 1.
+ *
+ * Think of this operation as an atomic version of
+ * { *atomic -= 1; return *atomic == 0; }
+ *
+ * This call acts as a full compiler and hardware memory barrier.
+ */
+bool virAtomicIntDecAndTest(volatile int *atomic)
+    ATTRIBUTE_NONNULL(1);
+
+/**
+ * virAtomicIntCompareExchange:
+ * Compares atomic to oldval and, if equal, sets it to newval. If
+ * atomic was not equal to oldval then no change occurs.
+ *
+ * This compare and exchange is done atomically.
+ *
+ * Think of this operation as an atomic version of
+ * { if (*atomic == oldval) { *atomic = newval; return true; }
+ *    else return false; }
+ *
+ * This call acts as a full compiler and hardware memory barrier.
+ */
+bool virAtomicIntCompareExchange(volatile int *atomic,
+                                 int oldval,
+                                 int newval)
+    ATTRIBUTE_NONNULL(1);
+
+/**
+ * virAtomicIntAdd:
+ * Atomically adds val to the value of atomic.
+ *
+ * Think of this operation as an atomic version of
+ * { tmp = *atomic; *atomic += val; return tmp; }
+ *
+ * This call acts as a full compiler and hardware memory barrier.
+ */
+int virAtomicIntAdd(volatile int *atomic,
+                    int val)
+    ATTRIBUTE_NONNULL(1);
+
+/**
+ * virAtomicIntAnd:
+ * Performs an atomic bitwise 'and' of the value of atomic
+ * and val, storing the result back in atomic.
+ *
+ * This call acts as a full compiler and hardware memory barrier.
+ *
+ * Think of this operation as an atomic version of
+ * { tmp = *atomic; *atomic &= val; return tmp; }
+ */
+unsigned int virAtomicIntAnd(volatile unsigned int *atomic,
+                             unsigned int val)
+    ATTRIBUTE_NONNULL(1);
+
+/**
+ * virAtomicIntOr:
+ * Performs an atomic bitwise 'or' of the value of atomic
+ * and val, storing the result back in atomic.
+ *
+ * Think of this operation as an atomic version of
+ * { tmp = *atomic; *atomic |= val; return tmp; }
+ *
+ * This call acts as a full compiler and hardware memory barrier.
+ */
+unsigned int virAtomicIntOr(volatile unsigned int *atomic,
+                            unsigned int val)
+    ATTRIBUTE_NONNULL(1);
+
+/**
+ * virAtomicIntXor:
+ * Performs an atomic bitwise 'xor' of the value of atomic
+ * and val, storing the result back in atomic.
+ *
+ * Think of this operation as an atomic version of
+ * { tmp = *atomic; *atomic ^= val; return tmp; }
+ *
+ * This call acts as a full compiler and hardware memory barrier.
+ */
+unsigned int virAtomicIntXor(volatile unsigned int *atomic,
+                             unsigned int val)
+    ATTRIBUTE_NONNULL(1);
+
+
+# ifdef VIR_ATOMIC_OPS_GCC
+
+#  define virAtomicIntGet(atomic)                                       \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));        \
+            (void)(0 ? *(atomic) ^ *(atomic) : 0);                      \
+            __sync_synchronize();                                       \
+            (int)*(atomic);                                             \
+        }))
+#  define virAtomicIntSet(atomic, newval)                               \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));        \
+            (void)(0 ? *(atomic) ^ (newval) : 0);                       \
+            *(atomic) = (newval);                                       \
+            __sync_synchronize();                                       \
+        }))
+#  define virAtomicIntInc(atomic)                                       \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));        \
+            (void)(0 ? *(atomic) ^ *(atomic) : 0);                      \
+            __sync_add_and_fetch((atomic), 1);                          \
+        }))
+#  define virAtomicIntDecAndTest(atomic)                                \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));        \
+            (void)(0 ? *(atomic) ^ *(atomic) : 0);                      \
+            __sync_fetch_and_sub((atomic), 1) == 1;                     \
+        }))
+#  define virAtomicIntCompareExchange(atomic, oldval, newval)           \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));        \
+            (void)(0 ? *(atomic) ^ (newval) ^ (oldval) : 0);            \
+            (bool)__sync_bool_compare_and_swap((atomic),                \
+                                               (oldval), (newval));     \
+        }))
+#  define virAtomicIntAdd(atomic, val)                                  \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));        \
+            (void)(0 ? *(atomic) ^ (val) : 0);                          \
+            (int) __sync_fetch_and_add((atomic), (val));                \
+        }))
+#  define virAtomicIntAnd(atomic, val)                                  \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));              \
+            (void) (0 ? *(atomic) ^ (val) : 0);                         \
+            (unsigned int) __sync_fetch_and_and((atomic), (val));       \
+        }))
+#  define virAtomicIntOr(atomic, val)                                   \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));              \
+            (void) (0 ? *(atomic) ^ (val) : 0);                         \
+            (unsigned int) __sync_fetch_and_or((atomic), (val));        \
+        }))
+#  define virAtomicIntXor(atomic, val)                                  \
+    (__extension__ ({                                                   \
+            (void)verify_true(sizeof(*(atomic)) == sizeof(int));              \
+            (void) (0 ? *(atomic) ^ (val) : 0);                         \
+            (unsigned int) __sync_fetch_and_xor((atomic), (val));       \
+        }))
+
+
+# else
+
+#  ifdef VIR_ATOMIC_OPS_WIN32
+
+#   include <winsock2.h>
+#   include <windows.h>
+#   include <intrin.h>
+#   if !defined(_M_AMD64) && !defined (_M_IA64) && !defined(_M_X64)
+#    define InterlockedAnd _InterlockedAnd
+#    define InterlockedOr _InterlockedOr
+#    define InterlockedXor _InterlockedXor
 #   endif
 
-static inline int virAtomicIntInit(virAtomicIntPtr vaip)
+/*
-    ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
+ * http://msdn.microsoft.com/en-us/library/ms684122(v=vs.85).aspx
-static inline int virAtomicIntRead(virAtomicIntPtr vaip)
+ */
-    ATTRIBUTE_NONNULL(1);
+inline int
-static inline void virAtomicIntSet(virAtomicIntPtr vaip, int val)
+virAtomicIntGet(volatile int *atomic)
-    ATTRIBUTE_NONNULL(1);
+{
-static inline int virAtomicIntAdd(virAtomicIntPtr vaip, int add)
+    MemoryBarrier();
-    ATTRIBUTE_NONNULL(1);
+    return *atomic;
-static inline int virAtomicIntSub(virAtomicIntPtr vaip, int add)
+}
-    ATTRIBUTE_NONNULL(1);
-static inline int virAtomicIntInc(virAtomicIntPtr vaip)
-    ATTRIBUTE_NONNULL(1);
-static inline int virAtomicIntDec(virAtomicIntPtr vaip)
-    ATTRIBUTE_NONNULL(1);
 
-# ifdef __VIR_ATOMIC_USES_LOCK
+inline void
+virAtomicIntSet(volatile int *atomic,
+                int newval)
+{
+    *atomic = newval;
+    MemoryBarrier();
+}
 
-struct _virAtomicInt {
+inline int
-    virMutex lock;
+virAtomicIntInc(volatile int *atomic)
+{
+    return InterlockedIncrement((volatile LONG *)atomic);
+}
+
+inline bool
+virAtomicIntDecAndTest(volatile int *atomic)
+{
+    return InterlockedDecrement((volatile LONG *)atomic) == 0;
+}
+
+inline bool
+virAtomicIntCompareExchange(volatile int *atomic,
+                            int oldval,
+                            int newval)
+{
+    return InterlockedCompareExchange((volatile LONG *)atomic, newval, oldval) == oldval;
+}
+
+inline int
+virAtomicIntAdd(volatile int *atomic,
+                int val)
+{
+    return InterlockedExchangeAdd((volatile LONG *)atomic, val);
+}
+
+inline unsigned int
+virAtomicIntAnd(volatile unsigned int *atomic,
+                unsigned int val)
+{
+    return InterlockedAnd((volatile LONG *)atomic, val);
+}
+
+inline unsigned int
+virAtomicIntOr(volatile unsigned int *atomic,
+               unsigned int val)
+{
+    return InterlockedOr((volatile LONG *)atomic, val);
+}
+
+inline unsigned int
+virAtomicIntXor(volatile unsigned int *atomic,
+                unsigned int val)
+{
+    return InterlockedXor((volatile LONG *)atomic, val);
+}
+
+
+#  else
+#   ifdef VIR_ATOMIC_OPS_PTHREAD
+#    include <pthread.h>
+
+extern pthread_mutex_t virAtomicLock;
+
+inline int
+virAtomicIntGet(volatile int *atomic)
+{
     int value;
-};
 
-static inline int
+    pthread_mutex_lock(&virAtomicLock);
-virAtomicIntInit(virAtomicIntPtr vaip)
+    value = *atomic;
-{
+    pthread_mutex_unlock(&virAtomicLock);
-    vaip->value = 0;
+
-    return virMutexInit(&vaip->lock);
+    return value;
 }
 
-static inline int
+inline void
-virAtomicIntAdd(virAtomicIntPtr vaip, int add)
+virAtomicIntSet(volatile int *atomic,
+                int value)
 {
-    int ret;
+    pthread_mutex_lock(&virAtomicLock);
-
+    *atomic = value;
-    virMutexLock(&vaip->lock);
+    pthread_mutex_unlock(&virAtomicLock);
-
-    vaip->value += add;
-    ret = vaip->value;
-
-    virMutexUnlock(&vaip->lock);
-
-    return ret;
 }
 
-static inline int
+inline int
-virAtomicIntSub(virAtomicIntPtr vaip, int sub)
+virAtomicIntInc(volatile int *atomic)
 {
-    int ret;
-
-    virMutexLock(&vaip->lock);
-
-    vaip->value -= sub;
-    ret = vaip->value;
-
-    virMutexUnlock(&vaip->lock);
-
-    return ret;
-}
-
-# else /* __VIR_ATOMIC_USES_LOCK */
-
-struct _virAtomicInt {
     int value;
-};
 
-static inline int
+    pthread_mutex_lock(&virAtomicLock);
-virAtomicIntInit(virAtomicIntPtr vaip)
+    value = ++(*atomic);
-{
+    pthread_mutex_unlock(&virAtomicLock);
-    vaip->value = 0;
+
-    return 0;
+    return value;
 }
 
-static inline int
+inline bool
-virAtomicIntAdd(virAtomicIntPtr vaip, int add)
+virAtomicIntDecAndTest(volatile int *atomic)
 {
-    return __sync_add_and_fetch(&vaip->value, add);
+    bool is_zero;
+
+    pthread_mutex_lock(&virAtomicLock);
+    is_zero = --(*atomic) == 0;
+    pthread_mutex_unlock(&virAtomicLock);
+
+    return is_zero;
 }
 
-static inline int
+inline bool
-virAtomicIntSub(virAtomicIntPtr vaip, int sub)
+virAtomicIntCompareExchange(volatile int *atomic,
+                            int oldval,
+                            int newval)
 {
-    return __sync_sub_and_fetch(&vaip->value, sub);
+    bool success;
+
+    pthread_mutex_lock(&virAtomicLock);
+
+    if ((success = (*atomic == oldval)))
+        *atomic = newval;
+
+    pthread_mutex_unlock(&virAtomicLock);
+
+    return success;
 }
 
-# endif /* __VIR_ATOMIC_USES_LOCK */
+inline int
-
+virAtomicIntAdd(volatile int *atomic,
-
+                int val)
-
-/* common operations that need no locking or build on others */
-
-
-static inline void
-virAtomicIntSet(virAtomicIntPtr vaip, int value)
 {
-     vaip->value = value;
+    int oldval;
+
+    pthread_mutex_lock(&virAtomicLock);
+    oldval = *atomic;
+    *atomic = oldval + val;
+    pthread_mutex_unlock(&virAtomicLock);
+
+    return oldval;
 }
 
-static inline int
+inline unsigned int
-virAtomicIntRead(virAtomicIntPtr vaip)
+virAtomicIntAnd(volatile unsigned int *atomic,
+                unsigned int val)
 {
-     return *(volatile int *)&vaip->value;
+    unsigned int oldval;
+
+    pthread_mutex_lock(&virAtomicLock);
+    oldval = *atomic;
+    *atomic = oldval & val;
+    pthread_mutex_unlock(&virAtomicLock);
+
+    return oldval;
 }
 
-static inline int
+inline unsigned int
-virAtomicIntInc(virAtomicIntPtr vaip)
+virAtomicIntOr(volatile unsigned int *atomic,
+               unsigned int val)
 {
-    return virAtomicIntAdd(vaip, 1);
+    unsigned int oldval;
+
+    pthread_mutex_lock(&virAtomicLock);
+    oldval = *atomic;
+    *atomic = oldval | val;
+    pthread_mutex_unlock(&virAtomicLock);
+
+    return oldval;
 }
 
-static inline int
+inline unsigned int
-virAtomicIntDec(virAtomicIntPtr vaip)
+virAtomicIntXor(volatile unsigned int *atomic,
+                unsigned int val)
 {
-    return virAtomicIntSub(vaip, 1);
+    unsigned int oldval;
+
+    pthread_mutex_lock(&virAtomicLock);
+    oldval = *atomic;
+    *atomic = oldval ^ val;
+    pthread_mutex_unlock(&virAtomicLock);
+
+    return oldval;
 }
 
+
+#   else
+#    error "No atomic integer impl for this platform"
+#   endif
+#  endif
+
+/* The int/unsigned int casts here ensure that you can
+ * pass either an int or unsigned int to all atomic op
+ * functions, in the same way that we can with GCC
+ * atomic op helpers.
+ */
+#  define virAtomicIntGet(atomic)               \
+    virAtomicIntGet((int *)atomic)
+#  define virAtomicIntSet(atomic, val)          \
+    virAtomicIntSet((int *)atomic, val)
+#  define virAtomicIntInc(atomic)               \
+    virAtomicIntInc((int *)atomic)
+#  define virAtomicIntDecAndTest(atomic)        \
+    virAtomicIntDecAndTest((int *)atomic)
+#  define virAtomicIntCompareExchange(atomic, oldval, newval)   \
+    virAtomicIntCompareExchange((int *)atomic, oldval, newval)
+#  define virAtomicIntAdd(atomic, val)          \
+    virAtomicIntAdd((int *)atomic, val)
+#  define virAtomicIntAnd(atomic, val)          \
+    virAtomicIntAnd((unsigned int *)atomic, val)
+#  define virAtomicIntOr(atomic, val)           \
+    virAtomicIntOr((unsigned int *)atomic, val)
+#  define virAtomicIntXor(atomic, val)          \
+    virAtomicIntXor((unsigned int *)atomic, val)
+
+# endif
+
 #endif /* __VIR_ATOMIC_H */

src/util/virfile.c

@@ -618,7 +618,7 @@ cleanup:
 #else /* __linux__ */
 
 int virFileLoopDeviceAssociate(const char *file,
-                               char **dev)
+                               char **dev ATTRIBUTE_UNUSED)
 {
     virReportSystemError(ENOSYS,
                          _("Unable to associate file %s with loop device"),

tests/Makefile.am

@@ -89,6 +89,7 @@ test_programs = virshtest sockettest \
 	nodeinfotest virbuftest \
 	commandtest seclabeltest \
 	virhashtest virnetmessagetest virnetsockettest \
+	viratomictest \
 	utiltest virnettlscontexttest shunloadtest \
 	virtimetest viruritest virkeyfiletest \
 	virauthconfigtest
@@ -530,6 +531,10 @@ virhashtest_SOURCES = \
 	virhashtest.c virhashdata.h testutils.h testutils.c
 virhashtest_LDADD = $(LDADDS)
 
+viratomictest_SOURCES = \
+	viratomictest.c viratomicdata.h testutils.h testutils.c
+viratomictest_LDADD = $(LDADDS)
+
 jsontest_SOURCES = \
 	jsontest.c testutils.h testutils.c
 jsontest_LDADD = $(LDADDS)

tests/viratomictest.c

@@ -0,0 +1,181 @@
+/*
+ * Copyright (C) 2011-2012 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * License along with this library;  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <config.h>
+
+#include <time.h>
+#include <sched.h>
+
+#include "testutils.h"
+
+#include "viratomic.h"
+#include "virrandom.h"
+#include "threads.h"
+
+static int
+testTypes(const void *data ATTRIBUTE_UNUSED)
+{
+    unsigned int u, u2;
+    int s, s2;
+    bool res;
+
+#define virAssertCmpInt(a, op, b) \
+    if (!((a) op (b))) \
+        return -1;
+    virAtomicIntSet(&u, 5);
+    u2 = virAtomicIntGet(&u);
+    virAssertCmpInt(u2, ==, 5);
+
+    res = virAtomicIntCompareExchange(&u, 6, 7);
+    if (res)
+        return -1;
+    virAssertCmpInt(u, ==, 5);
+
+    virAssertCmpInt(virAtomicIntAdd(&u, 1), ==, 5);
+    virAssertCmpInt(u, ==, 6);
+
+    virAssertCmpInt(virAtomicIntInc(&u), ==, 7);
+    virAssertCmpInt(u, ==, 7);
+
+    res = virAtomicIntDecAndTest(&u);
+    if (res)
+        return -1;
+    virAssertCmpInt(u, ==, 6);
+
+    u2 = virAtomicIntAnd(&u, 5);
+    virAssertCmpInt(u2, ==, 6);
+    virAssertCmpInt(u, ==, 4);
+
+    u2 = virAtomicIntOr(&u, 8);
+    virAssertCmpInt(u2, ==, 4);
+    virAssertCmpInt(u, ==, 12);
+
+    u2 = virAtomicIntXor(&u, 4);
+    virAssertCmpInt(u2, ==, 12);
+    virAssertCmpInt(u, ==, 8);
+
+    virAtomicIntSet(&s, 5);
+    s2 = virAtomicIntGet(&s);
+    virAssertCmpInt(s2, ==, 5);
+
+    res = virAtomicIntCompareExchange(&s, 6, 7);
+    if (res)
+        return -1;
+    virAssertCmpInt(s, ==, 5);
+
+    virAtomicIntAdd(&s, 1);
+    virAssertCmpInt(s, ==, 6);
+
+    virAtomicIntInc(&s);
+    virAssertCmpInt(s, ==, 7);
+
+    res = virAtomicIntDecAndTest(&s);
+    if (res)
+        return -1;
+    virAssertCmpInt(s, ==, 6);
+
+    s2 = virAtomicIntAnd(&s, 5);
+    virAssertCmpInt(s2, ==, 6);
+    virAssertCmpInt(s, ==, 4);
+
+    s2 = virAtomicIntOr(&s, 8);
+    virAssertCmpInt(s2, ==, 4);
+    virAssertCmpInt(s, ==, 12);
+
+    s2 = virAtomicIntXor(&s, 4);
+    virAssertCmpInt(s2, ==, 12);
+    virAssertCmpInt(s, ==, 8);
+
+    return 0;
+}
+
+#define THREADS 10
+#define ROUNDS 10000
+
+volatile int bucket[THREADS];
+volatile int atomic;
+
+static void
+thread_func(void *data)
+{
+    int idx = (int)(long)data;
+    int i;
+    int d;
+
+    for (i = 0; i < ROUNDS; i++) {
+        d = virRandomBits(7);
+        bucket[idx] += d;
+        virAtomicIntAdd(&atomic, d);
+#ifdef WIN32
+        SleepEx(0,0);
+#else
+        sched_yield();
+#endif
+    }
+}
+
+static int
+testThreads(const void *data ATTRIBUTE_UNUSED)
+{
+    int sum;
+    int i;
+    virThread threads[THREADS];
+
+    atomic = 0;
+    for (i = 0; i < THREADS; i++)
+        bucket[i] = 0;
+
+    for (i = 0; i < THREADS; i++) {
+        if (virThreadCreate(&(threads[i]), true, thread_func, (void*)(long)i) < 0)
+            return -1;
+    }
+
+    for (i = 0; i < THREADS; i++)
+        virThreadJoin(&threads[i]);
+
+    sum = 0;
+    for (i = 0; i < THREADS; i++)
+        sum += bucket[i];
+
+    if (sum != atomic)
+        return -1;
+
+    return 0;
+}
+
+static int
+mymain(void)
+{
+    int ret = 0;
+
+    if (virRandomInitialize(time(NULL)) < 0)
+        return -1;
+    if (virThreadInitialize() < 0)
+        return -1;
+
+    if (virtTestRun("types", 1, testTypes, NULL) < 0)
+        ret = -1;
+    if (virtTestRun("threads", 1, testThreads, NULL) < 0)
+        ret = -1;
+
+    return ret;
+}
+
+VIRT_TEST_MAIN(mymain)