This patch tries to address some of the apr_atomic problems by reorganizing

the various backends. The generic implementation is used when no specialized
implementation fits the defined criterias, or when the user forces the choice.

PR: 42806


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@553289 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 192 insertions, 464 deletions

diff --git a/atomic/unix/apr_atomic.c b/atomic/unix/apr_atomic.c
deleted file mode 100644
index 2bd645e05..000000000
--- a/atomic/unix/apr_atomic.c
+++ /dev/null
@@ -1,464 +0,0 @@
-/* Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "apr.h"
-#include "apr_atomic.h"
-#include "apr_thread_mutex.h"
-
-#include "apr_private.h"
-
-#include <stdlib.h>
-#if (defined(SOLARIS2) && SOLARIS2 >= 10)
-#include <atomic.h>
-#endif
-
-#if defined(__GNUC__) && defined(__STRICT_ANSI__) && !defined(USE_GENERIC_ATOMICS)
-/* force use of generic atomics if building e.g. with -std=c89, which
- * doesn't allow inline asm */
-#define USE_GENERIC_ATOMICS
-#endif
-
-#if (defined(__i386__) || defined(__x86_64__)) \
-    && defined(__GNUC__) && !defined(USE_GENERIC_ATOMICS)
-
-APR_DECLARE(apr_uint32_t) apr_atomic_cas32(volatile apr_uint32_t *mem, 
-                                           apr_uint32_t with,
-                                           apr_uint32_t cmp)
-{
-    apr_uint32_t prev;
-
-    asm volatile ("lock; cmpxchgl %1, %2"             
-                  : "=a" (prev)               
-                  : "r" (with), "m" (*(mem)), "0"(cmp) 
-                  : "memory", "cc");
-    return prev;
-}
-#define APR_OVERRIDE_ATOMIC_CAS32
-
-static apr_uint32_t inline intel_atomic_add32(volatile apr_uint32_t *mem, 
-                                              apr_uint32_t val)
-{
-    asm volatile ("lock; xaddl %0,%1"
-                  : "=r"(val), "=m"(*mem) /* outputs */
-                  : "0"(val), "m"(*mem)   /* inputs */
-                  : "memory", "cc");
-    return val;
-}
-
-APR_DECLARE(apr_uint32_t) apr_atomic_add32(volatile apr_uint32_t *mem, 
-                                           apr_uint32_t val)
-{
-    return intel_atomic_add32(mem, val);
-}
-#define APR_OVERRIDE_ATOMIC_ADD32
-
-APR_DECLARE(void) apr_atomic_sub32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    asm volatile ("lock; subl %1, %0"
-                  :
-                  : "m" (*(mem)), "r" (val)
-                  : "memory", "cc");
-}
-#define APR_OVERRIDE_ATOMIC_SUB32
-
-APR_DECLARE(int) apr_atomic_dec32(volatile apr_uint32_t *mem)
-{
-    unsigned char prev;
-
-    asm volatile ("lock; decl %1;\n\t"
-                  "setnz %%al"
-                  : "=a" (prev)
-                  : "m" (*(mem))
-                  : "memory", "cc");
-    return prev;
-}
-#define APR_OVERRIDE_ATOMIC_DEC32
-
-APR_DECLARE(apr_uint32_t) apr_atomic_inc32(volatile apr_uint32_t *mem)
-{
-    return intel_atomic_add32(mem, 1);
-}
-#define APR_OVERRIDE_ATOMIC_INC32
-
-APR_DECLARE(void) apr_atomic_set32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    *mem = val;
-}
-#define APR_OVERRIDE_ATOMIC_SET32
-
-APR_DECLARE(apr_uint32_t) apr_atomic_xchg32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    apr_uint32_t prev = val;
-
-    asm volatile ("lock; xchgl %0, %1"
-                  : "=r" (prev)
-                  : "m" (*(mem)), "0"(prev)
-                  : "memory");
-    return prev;
-}
-#define APR_OVERRIDE_ATOMIC_XCHG32
-
-/*#define apr_atomic_init(pool)        APR_SUCCESS*/
-
-#endif /* (__linux__ || __EMX__ || __FreeBSD__) && __i386__ */
-
-#if (defined(__PPC__) || defined(__ppc__)) && defined(__GNUC__) \
-    && !defined(USE_GENERIC_ATOMICS)
-
-APR_DECLARE(apr_uint32_t) apr_atomic_cas32(volatile apr_uint32_t *mem,
-                                           apr_uint32_t swap,
-                                           apr_uint32_t cmp)
-{
-    apr_uint32_t prev;
-                                                                                
-    asm volatile ("0:\n\t"                   /* retry local label     */
-                  "lwarx  %0,0,%1\n\t"       /* load prev and reserve */
-                  "cmpw   %0,%3\n\t"         /* does it match cmp?    */
-                  "bne-   1f\n\t"            /* ...no, bail out       */
-                  "stwcx. %2,0,%1\n\t"       /* ...yes, conditionally
-                                                store swap            */
-                  "bne-   0b\n\t"            /* start over if we lost
-                                                the reservation       */
-                  "1:"                       /* exit local label      */
-
-                  : "=&r"(prev)                        /* output      */
-                  : "b" (mem), "r" (swap), "r"(cmp)    /* inputs      */
-                  : "memory", "cc");                   /* clobbered   */
-    return prev;
-}
-#define APR_OVERRIDE_ATOMIC_CAS32
-
-APR_DECLARE(apr_uint32_t) apr_atomic_add32(volatile apr_uint32_t *mem,
-                                           apr_uint32_t delta)
-{
-    apr_uint32_t prev, temp;
-                                                                                
-    asm volatile ("0:\n\t"                   /* retry local label     */
-                  "lwarx  %0,0,%2\n\t"       /* load prev and reserve */
-                  "add    %1,%0,%3\n\t"      /* temp = prev + delta   */
-                  "stwcx. %1,0,%2\n\t"       /* conditionally store   */
-                  "bne-   0b"                /* start over if we lost
-                                                the reservation       */
-
-                  /*XXX find a cleaner way to define the temp         
-                   *    it's not an output
-                   */
-                  : "=&r" (prev), "=&r" (temp)        /* output, temp */
-                  : "b" (mem), "r" (delta)            /* inputs       */
-                  : "memory", "cc");                  /* clobbered    */
-    return prev;
-}
-#define APR_OVERRIDE_ATOMIC_ADD32
-
-#endif /* __PPC__ && __GNUC__ */
-
-#if (defined(SOLARIS2) && SOLARIS2 >= 10) \
-    && !defined(USE_GENERIC_ATOMICS)
-
-#if !defined(APR_OVERRIDE_ATOMIC_CAS32)
-APR_DECLARE(apr_uint32_t) apr_atomic_cas32(volatile apr_uint32_t *mem,
-                                           apr_uint32_t with,
-                                           apr_uint32_t cmp)
-{
-    return atomic_cas_32(mem, cmp, with);
-}
-#define APR_OVERRIDE_ATOMIC_CAS32
-#endif /* APR_OVERRIDE_ATOMIC_CAS32 */
-
-#if !defined(APR_OVERRIDE_ATOMIC_DEC32)
-APR_DECLARE(int) apr_atomic_dec32(volatile apr_uint32_t *mem)
-{
-    apr_uint32_t prev = *mem;
-    atomic_dec_32(mem);
-    return prev != 1;
-}
-#define APR_OVERRIDE_ATOMIC_DEC32
-#endif /* APR_OVERRIDE_ATOMIC_DEC32 */
-
-#if !defined(APR_OVERRIDE_ATOMIC_INC32)
-APR_DECLARE(apr_uint32_t) apr_atomic_inc32(volatile apr_uint32_t *mem)
-{
-    apr_uint32_t prev = *mem;
-    atomic_inc_32(mem);
-    return prev;
-}
-#define APR_OVERRIDE_ATOMIC_INC32
-#endif /* APR_OVERRIDE_ATOMIC_INC32 */
-
-#if !defined(APR_OVERRIDE_ATOMIC_SET32)
-APR_DECLARE(void) apr_atomic_set32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    *mem = val;
-}
-#define APR_OVERRIDE_ATOMIC_SET32
-#endif /* APR_OVERRIDE_ATOMIC_SET32 */
-
-#if !defined(APR_OVERRIDE_ATOMIC_XCHG32)
-APR_DECLARE(apr_uint32_t) apr_atomic_xchg32(volatile apr_uint32_t *mem,
-                                            apr_uint32_t val) 
-{
-    return atomic_swap_32(mem, val);
-}
-#define APR_OVERRIDE_ATOMIC_XCHG32
-#endif /* APR_OVERRIDE_ATOMIC_XCHG32 */
-
-#endif /* SOLARIS2 && SOLARIS2 >= 10 */
-
-#if !defined(APR_OVERRIDE_ATOMIC_INIT)
-
-#if APR_HAS_THREADS
-#define NUM_ATOMIC_HASH 7
-/* shift by 2 to get rid of alignment issues */
-#define ATOMIC_HASH(x) (unsigned int)(((unsigned long)(x)>>2)%(unsigned int)NUM_ATOMIC_HASH)
-static apr_thread_mutex_t **hash_mutex;
-#endif /* APR_HAS_THREADS */
-
-#if APR_HAS_THREADS
-static apr_status_t atomic_cleanup(void *data)
-{
-    if (hash_mutex == data)
-        hash_mutex = NULL;
-
-    return APR_SUCCESS;
-}
-#endif
-
-apr_status_t apr_atomic_init(apr_pool_t *p)
-{
-#if APR_HAS_THREADS
-    int i;
-    apr_status_t rv;
-
-    if (hash_mutex != NULL)
-        return APR_SUCCESS;
-
-    hash_mutex = apr_palloc(p, sizeof(apr_thread_mutex_t*) * NUM_ATOMIC_HASH);
-    apr_pool_cleanup_register(p, hash_mutex, atomic_cleanup,
-                              apr_pool_cleanup_null);
-
-    for (i = 0; i < NUM_ATOMIC_HASH; i++) {
-        rv = apr_thread_mutex_create(&(hash_mutex[i]),
-                                     APR_THREAD_MUTEX_DEFAULT, p);
-        if (rv != APR_SUCCESS) {
-           return rv;
-        }
-    }
-#endif /* APR_HAS_THREADS */
-    return APR_SUCCESS;
-}
-#endif /* !defined(APR_OVERRIDE_ATOMIC_INIT) */
-
-/* abort() if 'x' does not evaluate to APR_SUCCESS. */
-#define CHECK(x) do { if ((x) != APR_SUCCESS) abort(); } while (0)
-
-#if !defined(APR_OVERRIDE_ATOMIC_ADD32)
-#if defined(APR_OVERRIDE_ATOMIC_CAS32)
-apr_uint32_t apr_atomic_add32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    apr_uint32_t old_value, new_value;
-    
-    do {
-        old_value = *mem;
-        new_value = old_value + val;
-    } while (apr_atomic_cas32(mem, new_value, old_value) != old_value);
-    return old_value;
-}
-#else
-apr_uint32_t apr_atomic_add32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    apr_uint32_t old_value;
-
-#if APR_HAS_THREADS
-    apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
-       
-    CHECK(apr_thread_mutex_lock(lock));
-    old_value = *mem;
-    *mem += val;
-    CHECK(apr_thread_mutex_unlock(lock));
-#else
-    old_value = *mem;
-    *mem += val;
-#endif /* APR_HAS_THREADS */
-    return old_value;
-}
-#endif /* defined(APR_OVERRIDE_ATOMIC_CAS32) */
-#endif /* !defined(APR_OVERRIDE_ATOMIC_ADD32) */
-
-#if !defined(APR_OVERRIDE_ATOMIC_SUB32)
-#if defined(APR_OVERRIDE_ATOMIC_CAS32)
-void apr_atomic_sub32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    apr_uint32_t old_value, new_value;
-    
-    do {
-        old_value = *mem;
-        new_value = old_value - val;
-    } while (apr_atomic_cas32(mem, new_value, old_value) != old_value);
-}
-#else
-void apr_atomic_sub32(volatile apr_uint32_t *mem, apr_uint32_t val) 
-{
-#if APR_HAS_THREADS
-    apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
-       
-    CHECK(apr_thread_mutex_lock(lock));
-    *mem -= val;
-    CHECK(apr_thread_mutex_unlock(lock));
-#else
-    *mem -= val;
-#endif /* APR_HAS_THREADS */
-}
-#endif /* defined(APR_OVERRIDE_ATOMIC_CAS32) */
-#endif /* !defined(APR_OVERRIDE_ATOMIC_SUB32) */
-
-#if !defined(APR_OVERRIDE_ATOMIC_SET32)
-void apr_atomic_set32(volatile apr_uint32_t *mem, apr_uint32_t val) 
-{
-#if APR_HAS_THREADS
-    apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
-
-    CHECK(apr_thread_mutex_lock(lock));
-    *mem = val;
-    CHECK(apr_thread_mutex_unlock(lock));
-#else
-    *mem = val;
-#endif /* APR_HAS_THREADS */
-}
-#endif /* !defined(APR_OVERRIDE_ATOMIC_SET32) */
-
-#if !defined(APR_OVERRIDE_ATOMIC_INC32)
-apr_uint32_t apr_atomic_inc32(volatile apr_uint32_t *mem) 
-{
-    return apr_atomic_add32(mem, 1);
-}
-#endif /* !defined(APR_OVERRIDE_ATOMIC_INC32) */
-
-#if !defined(APR_OVERRIDE_ATOMIC_DEC32)
-#if defined(APR_OVERRIDE_ATOMIC_CAS32)
-int apr_atomic_dec32(volatile apr_uint32_t *mem)
-{
-    apr_uint32_t old_value, new_value;
-    
-    do {
-        old_value = *mem;
-        new_value = old_value - 1;
-    } while (apr_atomic_cas32(mem, new_value, old_value) != old_value);
-    return old_value != 1;
-}
-#else
-int apr_atomic_dec32(volatile apr_uint32_t *mem) 
-{
-#if APR_HAS_THREADS
-    apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
-    apr_uint32_t new;
-
-    CHECK(apr_thread_mutex_lock(lock));
-    (*mem)--;
-    new = *mem;
-    CHECK(apr_thread_mutex_unlock(lock));
-    return new;
-#else
-    (*mem)--;
-    return *mem; 
-#endif /* APR_HAS_THREADS */
-}
-#endif /* defined(APR_OVERRIDE_ATOMIC_CAS32) */
-#endif /* !defined(APR_OVERRIDE_ATOMIC_DEC32) */
-
-#if !defined(APR_OVERRIDE_ATOMIC_CAS32)
-apr_uint32_t apr_atomic_cas32(volatile apr_uint32_t *mem, apr_uint32_t with,
-			      apr_uint32_t cmp)
-{
-    apr_uint32_t prev;
-#if APR_HAS_THREADS
-    apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
-
-    CHECK(apr_thread_mutex_lock(lock));
-    prev = *mem;
-    if (prev == cmp) {
-        *mem = with;
-    }
-    CHECK(apr_thread_mutex_unlock(lock));
-#else
-    prev = *mem;
-    if (prev == cmp) {
-        *mem = with;
-    }
-#endif /* APR_HAS_THREADS */
-    return prev;
-}
-#endif /* !defined(APR_OVERRIDE_ATOMIC_CAS32) */
-
-#if !defined(APR_OVERRIDE_ATOMIC_XCHG32)
-#if defined(APR_OVERRIDE_ATOMIC_CAS32)
-apr_uint32_t apr_atomic_xchg32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    apr_uint32_t prev;
-    do {
-        prev = *mem;
-    } while (apr_atomic_cas32(mem, val, prev) != prev);
-    return prev;
-}
-#else
-apr_uint32_t apr_atomic_xchg32(volatile apr_uint32_t *mem, apr_uint32_t val)
-{
-    apr_uint32_t prev;
-#if APR_HAS_THREADS
-    apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
-
-    CHECK(apr_thread_mutex_lock(lock));
-    prev = *mem;
-    *mem = val;
-    CHECK(apr_thread_mutex_unlock(lock));
-#else
-    prev = *mem;
-    *mem = val;
-#endif /* APR_HAS_THREADS */
-    return prev;
-}
-#endif /* defined(APR_OVERRIDE_ATOMIC_CAS32) */
-#endif /* !defined(APR_OVERRIDE_ATOMIC_XCHG32) */
-
-#if !defined(APR_OVERRIDE_ATOMIC_CASPTR)
-void *apr_atomic_casptr(volatile void **mem, void *with, const void *cmp)
-{
-    void *prev;
-#if APR_HAS_THREADS
-    apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
-
-    CHECK(apr_thread_mutex_lock(lock));
-    prev = *(void **)mem;
-    if (prev == cmp) {
-        *mem = with;
-    }
-    CHECK(apr_thread_mutex_unlock(lock));
-#else
-    prev = *(void **)mem;
-    if (prev == cmp) {
-        *mem = with;
-    }
-#endif /* APR_HAS_THREADS */
-    return prev;
-}
-#endif /* !defined(APR_OVERRIDE_ATOMIC_CASPTR) */
-
-#if !defined(APR_OVERRIDE_ATOMIC_READ32)
-APR_DECLARE(apr_uint32_t) apr_atomic_read32(volatile apr_uint32_t *mem)
-{
-    return *mem;
-}
-#endif
-
diff --git a/atomic/unix/mutex.c b/atomic/unix/mutex.c
new file mode 100644
index 000000000..17b605fcd
--- /dev/null
+++ b/atomic/unix/mutex.c
@@ -0,0 +1,192 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "apr_arch_atomic.h"
+
+#ifdef USE_ATOMICS_GENERIC
+
+#include <stdlib.h>
+
+#if APR_HAS_THREADS
+#   define DECLARE_MUTEX_LOCKED(name, mem)  \
+        apr_thread_mutex_t *name = mutex_hash(mem)
+#   define MUTEX_UNLOCK(name)                                   \
+        do {                                                    \
+            if (apr_thread_mutex_unlock(name) != APR_SUCCESS)   \
+                abort();                                        \
+        } while (0)
+#else
+#   define DECLARE_MUTEX_LOCKED(name, mem)
+#   define MUTEX_UNLOCK(name)
+#   warning Be warned: using stubs for all atomic operations
+#endif
+
+#if APR_HAS_THREADS
+
+static apr_thread_mutex_t **hash_mutex;
+
+#define NUM_ATOMIC_HASH 7
+/* shift by 2 to get rid of alignment issues */
+#define ATOMIC_HASH(x) (unsigned int)(((unsigned long)(x)>>2)%(unsigned int)NUM_ATOMIC_HASH)
+
+static apr_status_t atomic_cleanup(void *data)
+{
+    if (hash_mutex == data)
+        hash_mutex = NULL;
+
+    return APR_SUCCESS;
+}
+
+APR_DECLARE(apr_status_t) apr_atomic_init(apr_pool_t *p)
+{
+    int i;
+    apr_status_t rv;
+
+    if (hash_mutex != NULL)
+        return APR_SUCCESS;
+
+    hash_mutex = apr_palloc(p, sizeof(apr_thread_mutex_t*) * NUM_ATOMIC_HASH);
+    apr_pool_cleanup_register(p, hash_mutex, atomic_cleanup,
+                              apr_pool_cleanup_null);
+
+    for (i = 0; i < NUM_ATOMIC_HASH; i++) {
+        rv = apr_thread_mutex_create(&(hash_mutex[i]),
+                                     APR_THREAD_MUTEX_DEFAULT, p);
+        if (rv != APR_SUCCESS) {
+           return rv;
+        }
+    }
+
+    return APR_SUCCESS;
+}
+
+static APR_INLINE apr_thread_mutex_t *mutex_hash(volatile apr_uint32_t *mem)
+{
+    apr_thread_mutex_t *mutex = hash_mutex[ATOMIC_HASH(mem)];
+
+    if (apr_thread_mutex_lock(mutex) != APR_SUCCESS) {
+        abort();
+    }
+
+    return mutex;
+}
+
+#else
+
+APR_DECLARE(apr_status_t) apr_atomic_init(apr_pool_t *p)
+{
+    return APR_SUCCESS;
+}
+
+#endif /* APR_HAS_THREADS */
+
+APR_DECLARE(apr_uint32_t) apr_atomic_read32(volatile apr_uint32_t *mem)
+{
+    return *mem;
+}
+
+APR_DECLARE(void) apr_atomic_set32(volatile apr_uint32_t *mem, apr_uint32_t val)
+{
+    DECLARE_MUTEX_LOCKED(mutex, mem);
+
+    *mem = val;
+
+    MUTEX_UNLOCK(mutex);
+}
+
+APR_DECLARE(apr_uint32_t) apr_atomic_add32(volatile apr_uint32_t *mem, apr_uint32_t val)
+{
+    apr_uint32_t old_value;
+    DECLARE_MUTEX_LOCKED(mutex, mem);
+
+    old_value = *mem;
+    *mem += val;
+
+    MUTEX_UNLOCK(mutex);
+
+    return old_value;
+}
+
+APR_DECLARE(void) apr_atomic_sub32(volatile apr_uint32_t *mem, apr_uint32_t val)
+{
+    DECLARE_MUTEX_LOCKED(mutex, mem);
+    *mem -= val;
+    MUTEX_UNLOCK(mutex);
+}
+
+APR_DECLARE(apr_uint32_t) apr_atomic_inc32(volatile apr_uint32_t *mem)
+{
+    return apr_atomic_add32(mem, 1);
+}
+
+APR_DECLARE(int) apr_atomic_dec32(volatile apr_uint32_t *mem)
+{
+    apr_uint32_t new;
+    DECLARE_MUTEX_LOCKED(mutex, mem);
+
+    (*mem)--;
+    new = *mem;
+
+    MUTEX_UNLOCK(mutex);
+
+    return new;
+}
+
+APR_DECLARE(apr_uint32_t) apr_atomic_cas32(volatile apr_uint32_t *mem, apr_uint32_t with,
+                              apr_uint32_t cmp)
+{
+    apr_uint32_t prev;
+    DECLARE_MUTEX_LOCKED(mutex, mem);
+
+    prev = *mem;
+    if (prev == cmp) {
+        *mem = with;
+    }
+
+    MUTEX_UNLOCK(mutex);
+
+    return prev;
+}
+
+APR_DECLARE(apr_uint32_t) apr_atomic_xchg32(volatile apr_uint32_t *mem, apr_uint32_t val)
+{
+    apr_uint32_t prev;
+    DECLARE_MUTEX_LOCKED(mutex, mem);
+
+    prev = *mem;
+    *mem = val;
+
+    MUTEX_UNLOCK(mutex);
+
+    return prev;
+}
+
+APR_DECLARE(void*) apr_atomic_casptr(volatile void **mem, void *with, const void *cmp)
+{
+    void *prev;
+    DECLARE_MUTEX_LOCKED(mutex, *mem);
+
+    prev = *(void **)mem;
+    if (prev == cmp) {
+        *mem = with;
+    }
+
+    MUTEX_UNLOCK(mutex);
+
+    return prev;
+}
+
+#endif /* USE_ATOMICS_GENERIC */