Cleaner mechanism for using platform-specific atomics on platforms

that override some of the default atomic functions but not others


git-svn-id: http://svn.apache.org/repos/asf/apr/apr/trunk@63842 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 102 insertions, 44 deletions

diff --git a/atomic/unix/apr_atomic.c b/atomic/unix/apr_atomic.c
index a17e1adaa..e28d0f94c 100644
--- a/atomic/unix/apr_atomic.c
+++ b/atomic/unix/apr_atomic.c
@@ -56,17 +56,18 @@
 #include "apr_atomic.h"
 #include "apr_thread_mutex.h"
 
-#if APR_HAS_THREADS
-
-#if defined(APR_ATOMIC_NEED_DEFAULT) || defined(APR_ATOMIC_NEED_CAS_DEFAULT)
+#if !defined(apr_atomic_init) && !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 */
 
 apr_status_t apr_atomic_init(apr_pool_t *p)
 {
+#if APR_HAS_THREADS
     int i;
     apr_status_t rv;
     hash_mutex = apr_palloc(p, sizeof(apr_thread_mutex_t*) * NUM_ATOMIC_HASH);
@@ -78,13 +79,15 @@ apr_status_t apr_atomic_init(apr_pool_t *p)
            return rv;
         }
     }
+#endif /* APR_HAS_THREADS */
     return APR_SUCCESS;
 }
-#endif /* APR_ATOMIC_NEED_DEFAULT || APR_ATOMIC_NEED_CAS_DEFAULT */
+#endif /*!defined(apr_atomic_init) && !defined(APR_OVERRIDE_ATOMIC_INIT) */
 
-#if defined(APR_ATOMIC_NEED_DEFAULT) 
+#if !defined(apr_atomic_add) && !defined(APR_OVERRIDE_ATOMIC_ADD)
 void apr_atomic_add(volatile apr_atomic_t *mem, apr_uint32_t val) 
 {
+#if APR_HAS_THREADS
     apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
     apr_uint32_t prev;
        
@@ -93,10 +96,16 @@ void apr_atomic_add(volatile apr_atomic_t *mem, apr_uint32_t val)
         *mem += val;
         apr_thread_mutex_unlock(lock);
     }
+#else
+    *mem += val;
+#endif /* APR_HAS_THREADS */
 }
+#endif /*!defined(apr_atomic_add) && !defined(APR_OVERRIDE_ATOMIC_ADD) */
 
+#if !defined(apr_atomic_set) && !defined(APR_OVERRIDE_ATOMIC_SET)
 void apr_atomic_set(volatile apr_atomic_t *mem, apr_uint32_t val) 
 {
+#if APR_HAS_THREADS
     apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
     apr_uint32_t prev;
 
@@ -105,10 +114,16 @@ void apr_atomic_set(volatile apr_atomic_t *mem, apr_uint32_t val)
         *mem = val;
         apr_thread_mutex_unlock(lock);
     }
+#else
+    *mem = val;
+#endif /* APR_HAS_THREADS */
 }
+#endif /*!defined(apr_atomic_set) && !defined(APR_OVERRIDE_ATOMIC_SET) */
 
+#if !defined(apr_atomic_inc) && !defined(APR_OVERRIDE_ATOMIC_INC)
 void apr_atomic_inc(volatile apr_uint32_t *mem) 
 {
+#if APR_HAS_THREADS
     apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
     apr_uint32_t prev;
 
@@ -117,10 +132,16 @@ void apr_atomic_inc(volatile apr_uint32_t *mem)
         (*mem)++;
         apr_thread_mutex_unlock(lock);
     }
+#else
+    (*mem)++;
+#endif /* APR_HAS_THREADS */
 }
+#endif /*!defined(apr_atomic_inc) && !defined(APR_OVERRIDE_ATOMIC_INC) */
 
+#if !defined(apr_atomic_dec) && !defined(APR_OVERRIDE_ATOMIC_DEC)
 int apr_atomic_dec(volatile apr_atomic_t *mem) 
 {
+#if APR_HAS_THREADS
     apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
     apr_uint32_t new;
 
@@ -130,14 +151,17 @@ int apr_atomic_dec(volatile apr_atomic_t *mem)
         apr_thread_mutex_unlock(lock);
         return new; 
     }
+#else
+    (*mem)--;
+#endif /* APR_HAS_THREADS */
     return *mem; 
 }
+#endif /*!defined(apr_atomic_dec) && !defined(APR_OVERRIDE_ATOMIC_DEC) */
 
-#endif /* APR_ATOMIC_NEED_DEFAULT */
-#if defined(APR_ATOMIC_NEED_CAS_DEFAULT)
-
+#if !defined(apr_atomic_cas) && !defined(APR_OVERRIDE_ATOMIC_CASE)
 apr_uint32_t apr_atomic_cas(volatile apr_uint32_t *mem, long with, long cmp)
 {
+#if APR_HAS_THREADS
     apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
     long prev;
 
@@ -150,16 +174,12 @@ apr_uint32_t apr_atomic_cas(volatile apr_uint32_t *mem, long with, long cmp)
         return prev;
     }
     return *(long*)mem;
-}
-#endif /* APR_ATOMIC_NEED_CAS_DEFAULT */
-
-#else /* !APR_HAS_THREADS */
-
-#if !defined(apr_atomic_init)
-apr_status_t apr_atomic_init(apr_pool_t *p)
-{
-    return APR_SUCCESS;
-}
-#endif /* !defined(apr_atomic_init) */
-
+#else
+    prev = *(long*)mem;
+    if ( prev == cmp) {
+        *(long*)mem = with;
+    }
+    return prev;
 #endif /* APR_HAS_THREADS */
+}
+#endif /*!defined(apr_atomic_dec) && !defined(APR_OVERRIDE_ATOMIC_DEC) */
diff --git a/include/apr_atomic.h b/include/apr_atomic.h
index 9277658cf..e9189aa56 100644
--- a/include/apr_atomic.h
+++ b/include/apr_atomic.h
@@ -136,13 +136,14 @@ int apr_atomic_dec(volatile apr_atomic_t *mem);
 apr_uint32_t apr_atomic_cas(volatile apr_uint32_t *mem,long with,long cmp);
 #else /* !DOXYGEN */
 
-#if APR_FORCE_ATOMIC_GENERIC 
-#if APR_HAS_THREADS
-#define APR_ATOMIC_NEED_DEFAULT 1
-#define APR_ATOMIC_NEED_CAS_DEFAULT 1
-#endif /* APR_HAS_THREADS */
+/* The following definitions provide optimized, OS-specific
+ * implementations of the APR atomic functions on various
+ * platforms.  Any atomic operation that isn't redefined as
+ * a macro here will be declared as a function later, and
+ * apr_atomic.c will provide a mutex-based default implementation.
+ */
 
-#elif defined(WIN32)
+#if defined(WIN32)
 
 typedef LONG apr_atomic_t;
 
@@ -161,6 +162,7 @@ typedef LONG apr_atomic_t;
 
 #define apr_atomic_add(mem, val)     atomic_add(mem,val)
 APR_DECLARE(int) apr_atomic_dec(apr_atomic_t *mem);
+#define APR_OVERRIDE_ATOMIC_DEC 1
 #define apr_atomic_inc(mem)          atomic_inc(mem)
 #define apr_atomic_set(mem, val)     (*mem = val)
 #define apr_atomic_read(mem)         (*mem)
@@ -178,9 +180,8 @@ APR_DECLARE(int) apr_atomic_dec(apr_atomic_t *mem);
 #define apr_atomic_set(mem, val)     atomic_set_int(mem, val)
 #define apr_atomic_read(mem)         (*mem)
 
-#define APR_ATOMIC_NEED_CAS_DEFAULT 1
+#elif defined(__linux__) && defined(__i386__) && !APR_FORCE_ATOMIC_GENERIC
 
-#elif defined(__linux__) && defined(__i386__)
 #define apr_atomic_t apr_uint32_t
 #define apr_atomic_cas(mem,with,cmp) \
 ({ apr_atomic_t prev; \
@@ -190,12 +191,8 @@ APR_DECLARE(int) apr_atomic_dec(apr_atomic_t *mem);
          : "memory"); \
     prev;})
 
-#define APR_ATOMIC_NEED_DEFAULT 1
-#if defined(APR_ATOMIC_NEED_CAS_DEFAULT)
-#undef APR_ATOMIC_NEED_CAS_DEFAULT
-#endif
+#elif defined(__sparc__) || defined(sparc) && !APR_FORCE_ATOMIC_GENERIC
 
-#elif defined(__sparc__) || defined(sparc)
 #define apr_atomic_t apr_uint32_t
 #define apr_atomic_read(p)  *p
 
@@ -217,6 +214,8 @@ apr_uint32_t apr_atomic_cas_sparc(volatile apr_uint32_t *mem, long with, long cm
 apr_int32_t apr_atomic_add(volatile apr_atomic_t *mem, apr_int32_t val);
 apr_uint32_t apr_atomic_cas(volatile apr_atomic_t *mem, apr_uint32_t swap, 
                             apr_uint32_t cmp);
+#define APR_OVERRIDE_ATOMIC_ADD 1
+#define APR_OVERRIDE_ATOMIC_CAS 1
 
 #define apr_atomic_inc(mem)          apr_atomic_add(mem, 1)
 #define apr_atomic_dec(mem)          apr_atomic_add(mem, -1)
@@ -234,30 +233,69 @@ apr_uint32_t apr_atomic_cas(volatile apr_atomic_t *mem, apr_uint32_t swap,
 #define apr_atomic_read(p)           (*p)
 #define apr_atomic_set(mem, val)     (*mem = val)
 
-#else
-#if APR_HAS_THREADS
-#define APR_ATOMIC_NEED_DEFAULT 1
-#define APR_ATOMIC_NEED_CAS_DEFAULT 1
-#endif /* APR_HAS_THREADS */
+#endif /* end big if-elseif switch for platform-specifics */
+
 
-#endif /* !defined(WIN32) */
+/* Default implementation of the atomic API
+ * The definitions above may override some or all of the
+ * atomic functions with optimized, platform-specific versions.
+ * Any operation that hasn't been overridden as a macro above
+ * is declared as a function here, unless APR_OVERRIDE_ATOMIC_[OPERATION]
+ * is defined.  (The purpose of the APR_OVERRIDE_ATOMIC_* is
+ * to allow a platform to declare an apr_atomic_*() function
+ * with a different signature than the default.)
+ */
+
+#define APR_ATOMIC_NEED_DEFAULT_INIT 0
 
-#if defined(APR_ATOMIC_NEED_DEFAULT)
+#if !defined(apr_atomic_t)
 #define apr_atomic_t apr_uint32_t
-#define apr_atomic_read(p)  *p
+#endif
+
+#if !defined(apr_atomic_init) && !defined(APR_OVERRIDE_ATOMIC_INIT)
 apr_status_t apr_atomic_init(apr_pool_t *p);
+#endif
+
+#if !defined(apr_atomic_read) && !defined(APR_OVERRIDE_ATOMIC_READ)
+#define apr_atomic_read(p)  *p
+#endif
+
+#if !defined(apr_atomic_set) && !defined(APR_OVERRIDE_ATOMIC_SET)
 void apr_atomic_set(volatile apr_atomic_t *mem, apr_uint32_t val);
+#define APR_ATOMIC_NEED_DEFAULT_INIT 1
+#endif
+
+#if !defined(apr_atomic_add) && !defined(APR_OVERRIDE_ATOMIC_ADD)
 void apr_atomic_add(volatile apr_atomic_t *mem, apr_uint32_t val);
+#define APR_ATOMIC_NEED_DEFAULT_INIT 1
+#endif
+
+#if !defined(apr_atomic_inc) && !defined(APR_OVERRIDE_ATOMIC_INC)
 void apr_atomic_inc(volatile apr_atomic_t *mem);
+#define APR_ATOMIC_NEED_DEFAULT_INIT 1
+#endif
+
+#if !defined(apr_atomic_dec) && !defined(APR_OVERRIDE_ATOMIC_DEC)
 int apr_atomic_dec(volatile apr_atomic_t *mem);
+#define APR_ATOMIC_NEED_DEFAULT_INIT 1
 #endif
 
-#if defined(APR_ATOMIC_NEED_CAS_DEFAULT)
-apr_status_t apr_atomic_init(apr_pool_t *p);
+#if !defined(apr_atomic_cas) && !defined(APR_OVERRIDE_ATOMIC_CAS)
 apr_uint32_t apr_atomic_cas(volatile apr_uint32_t *mem,long with,long cmp);
+#define APR_ATOMIC_NEED_DEFAULT_INIT 1
+#endif
+
+/* If we're using the default versions of any of the atomic functions,
+ * we'll need the atomic init to set up mutexes.  If a platform-specific
+ * override above has replaced the atomic_init with a macro, it's an error.
+ */
+#if APR_ATOMIC_NEED_DEFAULT_INIT
+#if defined(apr_atomic_init) || defined(APR_OVERRIDE_ATOMIC_INIT)
+#error Platform has redefined apr_atomic_init, but other default default atomics require a default apr_atomic_init
 #endif
+#endif /* APR_ATOMIC_NEED_DEFAULT_INIT */
 
-#endif /* DOXYGEN */
+#endif /* !DOXYGEN */
 #ifdef __cplusplus
 }
 #endif