diff --git a/arch/linux/common/tos_cpu.c b/arch/linux/common/tos_cpu.c
index d1b16e22..aa600949 100644
--- a/arch/linux/common/tos_cpu.c
+++ b/arch/linux/common/tos_cpu.c
@@ -78,6 +78,7 @@ __API__ void tos_cpu_cpsr_restore(cpu_cpsr_t cpsr)
 
 __KERNEL__ void cpu_init(void)
 {
+    port_init();
     k_cpu_cycle_per_tick = TOS_CFG_CPU_CLOCK / k_cpu_tick_per_second;
     cpu_systick_init(k_cpu_cycle_per_tick);
 
@@ -108,7 +109,6 @@ __KERNEL__ void cpu_irq_context_switch(void)
 
 __KERNEL__ void cpu_systick_init(k_cycle_t cycle_per_tick)
 {
-    port_systick_priority_set(TOS_CFG_CPU_SYSTICK_PRIO);
     port_systick_config(cycle_per_tick);
 }
 
diff --git a/arch/linux/posix/gcc/port.c b/arch/linux/posix/gcc/port.c
index bb7fb64d..ee199d31 100644
--- a/arch/linux/posix/gcc/port.c
+++ b/arch/linux/posix/gcc/port.c
@@ -81,17 +81,23 @@ interrupt_manager _int_manager={
 };
 
 static uint64_t tick_ms = 0;
+static pthread_t main_thread_id;
+static pthread_mutex_t cpsr_mutex;
+
+#define CHECK_IS_MAIN_THREAD(main_thread_id) \
+    if(main_thread_id != pthread_self()) return
 
 __PORT__ void port_int_disable(void)
 {
     sigset_t signal_mask,*manager_mask=NULL;
     if(_int_manager.count == 0){
+        pthread_mutex_lock(&cpsr_mutex);
         manager_mask = &(_int_manager.signal_mask);
+        sigfillset(&signal_mask);
+        _filter_signal(&signal_mask);
+        pthread_sigmask(SIG_BLOCK,&signal_mask,manager_mask);
     }
     _int_manager.count ++;
-    sigfillset(&signal_mask);
-    _filter_signal(&signal_mask);
-    pthread_sigmask(SIG_BLOCK,&signal_mask,manager_mask);
 }
 
 __PORT__ void port_int_enable(void)
@@ -102,6 +108,7 @@ __PORT__ void port_int_enable(void)
     if(_int_manager.count == 0){
         sigaddset(&(_int_manager.signal_mask),SIG_RESUME); //ensure SIG_RESUME is blocked
         _filter_signal(&(_int_manager.signal_mask));
+        pthread_mutex_unlock(&cpsr_mutex);
         pthread_sigmask(SIG_SETMASK,&(_int_manager.signal_mask),NULL);
     }
 }
@@ -126,10 +133,6 @@ __PORT__ pthread_t  port_create_thread(void *arg)
 
 __PORT__ void port_sched_start(void) 
 {
-    _install_signal(SIG_SUSPEND, _handle_suspend_thread);
-    _install_signal(SIG_RESUME, _handle_resume_thread);
-    _install_signal(SIG_CONTEXT_SWITCH, _handle_context_switch);
-
     k_curr_task = k_next_task;
     _resume_task(k_curr_task);
 
@@ -184,8 +187,13 @@ __PORT__ void port_systick_config(uint32_t cycle_per_tick)
 	}
 }
 
-__PORT__ void port_systick_priority_set(uint32_t prio)
+__PORT__ void port_init(void)
 {
+    main_thread_id = pthread_self();
+    pthread_mutex_init(&cpsr_mutex,NULL);
+    _install_signal(SIG_SUSPEND, _handle_suspend_thread);
+    _install_signal(SIG_RESUME, _handle_resume_thread);
+    _install_signal(SIG_CONTEXT_SWITCH, _handle_context_switch);
 }
 
 __PORT__ void port_delay_ms(uint32_t ms) 
@@ -224,6 +232,7 @@ __PORT__ void _install_signal(int sig,void (*func)(int))
 
 __PORT__ void _handle_tick_signal()
 {
+    CHECK_IS_MAIN_THREAD(main_thread_id);
     tick_ms ++;
     if(tos_knl_is_running()) {
         tos_knl_irq_enter();
diff --git a/arch/linux/posix/gcc/port.h b/arch/linux/posix/gcc/port.h
index 97d8ee83..a8f0f28e 100644
--- a/arch/linux/posix/gcc/port.h
+++ b/arch/linux/posix/gcc/port.h
@@ -89,7 +89,7 @@ __PORT__ void       port_irq_context_switch(void);
 
 __PORT__ void       port_systick_config(uint32_t cycle_per_tick);
 
-__PORT__ void       port_systick_priority_set(uint32_t prio);  //ok
+__PORT__ void       port_init(void);
 
 __PORT__ pthread_t  port_create_thread(void *arg);
 
diff --git a/board/Linux_Posix/mqtt_demo/src/socket_wrapper.c b/board/Linux_Posix/mqtt_demo/src/socket_wrapper.c
index 99867790..8ee2b3cd 100644
--- a/board/Linux_Posix/mqtt_demo/src/socket_wrapper.c
+++ b/board/Linux_Posix/mqtt_demo/src/socket_wrapper.c
@@ -12,12 +12,25 @@ static osMutexId socket_send_lock, socket_recv_lock;
 osMutexDef(socket_send_lock);
 osMutexDef(socket_recv_lock);
 
+static osSemaphoreId socket_recv_event;
+osSemaphoreDef(socket_recv_event);
+
 int socket_init(void)
 {
     socket_send_lock = osMutexCreate(osMutex(socket_send_lock));
     socket_recv_lock = osMutexCreate(osMutex(socket_recv_lock));
+    socket_recv_event = osSemaphoreCreate(osSemaphore(socket_recv_event),0);
 
-    return ((socket_recv_lock != NULL) && (socket_send_lock != NULL));
+    return (
+        (socket_recv_event != NULL) && 
+        (socket_recv_lock != NULL) && 
+        (socket_send_lock != NULL)
+    );
+}
+
+void io_signal_handle(int signal)
+{
+    osSemaphoreRelease(socket_recv_event);
 }
 
 int socket_connect(const char *ip, const char *port, sal_proto_t proto)
@@ -26,6 +39,7 @@ int socket_connect(const char *ip, const char *port, sal_proto_t proto)
         .sin_family = AF_INET,
         .sin_port = htons(atoi(port))};
     int socket_proto = 0;
+    struct sigaction sig_install;
 
     inet_pton(AF_INET, ip, &addr.sin_addr);
 
@@ -43,6 +57,19 @@ int socket_connect(const char *ip, const char *port, sal_proto_t proto)
     }
 
     int socket_id = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+    
+    fcntl( socket_id, __F_SETOWN, getpid() );
+    fcntl( socket_id, __F_SETSIG, SIGIO );
+    fcntl( socket_id, F_SETFL, O_ASYNC );
+
+    sig_install.sa_flags = 0;
+	sig_install.sa_handler = io_signal_handle;
+	sigfillset( &sig_install.sa_mask );
+
+    if ( 0 != sigaction( SIGIO, &sig_install, NULL ) )
+	{
+		printf( "socket problem installing %d\n",SIGIO );
+	}
 
     connect(socket_id, &addr, sizeof(addr));
     return socket_id;
@@ -63,7 +90,7 @@ int socket_send(int sock, const void *buf, size_t len)
         }
         if (send_len != len)
         {
-            osDelay(5);
+            osSemaphoreWait(socket_recv_event,100);
         }
     } while (len != send_len);
     osMutexRelease(socket_send_lock);
@@ -85,7 +112,7 @@ int socket_recv(int sock, void *buf, size_t len)
         }
         if (recv_len != len)
         {
-            osDelay(5);
+            osSemaphoreWait(socket_recv_event,100);
         }
     } while (len != recv_len);
     osMutexRelease(socket_recv_lock);