Socket: Use atomic operations instead of mutex

Signed-off-by: Vincent Coubard <vincent.coubard@arm.com>

bsp/aws_libraries/abstractions/secure_sockets/lwip/iot_secure_sockets.c

@@ -41,6 +41,8 @@
 #include <string.h>
 #include <stdbool.h>
 
+#include "bootstrap/mbed_atomic.h"
+
 /*-----------------------------------------------------------*/
 
 #define SS_STATUS_CONNECTED               ( 1 )
@@ -85,7 +87,6 @@ typedef struct _ss_ctx_t
     char ** ppcAlpnProtocols;
     uint32_t ulAlpnProtocolsCount;
     uint32_t ulRefcount;
-    osMutexId_t RefcountLock;
 } ss_ctx_t;
 
 /*-----------------------------------------------------------*/
@@ -151,11 +152,6 @@ static void prvSocketsClose( ss_ctx_t * ctx )
     {
         vPortFree( ctx->destination );
     }
-    
-    if ( ctx->RefcountLock )
-    {
-        osMutexDelete( ctx->RefcountLock );
-    }
 
     vPortFree( ctx );
 }
@@ -166,15 +162,9 @@ static void prvSocketsClose( ss_ctx_t * ctx )
  */
 static void prvDecrementRefCount( ss_ctx_t * ctx )
 {
-    osMutexAcquire( ctx->RefcountLock, osWaitForever );
-    ctx->ulRefcount -= 1;
-    if( ctx->ulRefcount == 0 )
-    {
+    if ( core_util_atomic_decr_u32( &ctx->ulRefcount, 1 ) ) {
         prvSocketsClose( ctx );
-        // do not release lock as it's been removed
-        return;
     }
-    osMutexRelease( ctx->RefcountLock );
 }
 
 /*
@@ -182,9 +172,7 @@ static void prvDecrementRefCount( ss_ctx_t * ctx )
  */
 static void prvIncrementRefCount( ss_ctx_t * ctx )
 {
-    osMutexAcquire( ctx->RefcountLock, osWaitForever );
-    ctx->ulRefcount += 1;
-    osMutexRelease( ctx->RefcountLock );
+    core_util_atomic_incr_u32( &ctx->ulRefcount, 1 );
 }
 
 /*
@@ -364,7 +352,6 @@ Socket_t SOCKETS_Socket( int32_t lDomain,
 
     if( ctx )
     {
-        ctx->RefcountLock = osMutexNew( NULL );
         memset( ctx, 0, sizeof( *ctx ) );
 
         ctx->ip_socket = iotSocketCreate( IOT_SOCKET_AF_INET, IOT_SOCKET_SOCK_STREAM, IOT_SOCKET_IPPROTO_TCP );