Merge pull request #11947 from gschorcht/cpu/esp32/freertos-critcial-sections

cpu/esp32: critcial section handling changed in FreeRTOS adaptation layer

cpu/esp32/Makefile

@@ -4,7 +4,6 @@ MODULE = cpu
 # Add a list of subdirectories, that should also be built:
 DIRS += $(RIOTCPU)/esp_common
 DIRS += periph
-DIRS += freertos
 DIRS += vendor
 
 ifneq (, $(filter esp_cxx, $(USEMODULE)))
@@ -23,4 +22,8 @@ ifneq (, $(filter esp_wifi, $(USEMODULE)))
     DIRS += esp-wifi
 endif
 
+ifneq (, $(filter riot_freertos, $(USEMODULE)))
+    DIRS += freertos
+endif
+
 include $(RIOTBASE)/Makefile.base

cpu/esp32/Makefile.include

@@ -79,6 +79,7 @@ USEMODULE += periph_hwrng
 USEMODULE += periph_flash
 USEMODULE += periph_rtc
 USEMODULE += periph_uart
+USEMODULE += riot_freertos
 USEMODULE += random
 USEMODULE += stdio_uart
 USEMODULE += xtensa

cpu/esp32/freertos/task.c

@@ -10,7 +10,7 @@
 
 #ifndef DOXYGEN
 
-#define ENABLE_DEBUG 0
+#define ENABLE_DEBUG (0)
 #include "debug.h"
 
 #include <string.h>
@@ -139,8 +139,14 @@ void vTaskEnterCritical( portMUX_TYPE *mux )
     /* disable interrupts */
     uint32_t state = irq_disable();
 
-    /* aquire the mutex with interrupts disabled */
-    mutex_lock(mux); /* TODO should be only a spin lock */
+    /* Locking the given mutex does not work here, as this function can also
+       be called in the interrupt context. Therefore, the given mutex is not
+       used. Instead, the basic default FreeRTOS mechanism for critical
+       sections is used by simply disabling interrupts. Since context
+       switches for the ESP32 are also based on interrupts, there is no
+       possibility that another thread will enter the critical section
+       once the interrupts are disabled. */
+    /* mutex_lock(mux); */ /* TODO should be only a spin lock */
 
     /* increment nesting counter and save old interrupt level */
     threads_arch_exts[my_pid].critical_nesting++;
@@ -157,8 +163,9 @@ void vTaskExitCritical( portMUX_TYPE *mux )
     DEBUG("%s pid=%d prio=%d mux=%p\n", __func__,
           my_pid, sched_threads[my_pid]->priority, mux);
 
-    /* release the mutex with interrupts disabled */
-    mutex_unlock(mux); /* TODO should be only a spin lock */
+    /* The given mutex is not used (see vTaskEnterCritical) and has not to
+       be unlocked here. */
+    /* mutex_unlock(mux); */ /* TODO should be only a spin lock */
 
     /* decrement nesting counter and restore old interrupt level */
     if (threads_arch_exts[my_pid].critical_nesting) {

cpu/esp32/include/freertos/portmacro.h

@@ -30,8 +30,8 @@ extern "C" {
 #define portMUX_TYPE                    mutex_t
 #define portMUX_INITIALIZER_UNLOCKED    MUTEX_INIT
 
-#define portENTER_CRITICAL(pm)          mutex_lock(pm)
-#define portEXIT_CRITICAL(pm)           mutex_unlock(pm)
+#define portENTER_CRITICAL(mux)         vTaskEnterCritical(mux)
+#define portEXIT_CRITICAL(mux)          vTaskExitCritical(mux)
 #define portENTER_CRITICAL_NESTED       irq_disable
 #define portEXIT_CRITICAL_NESTED        irq_restore
 
@@ -48,6 +48,9 @@ extern "C" {
 
 #define xPortGetCoreID()                PRO_CPU_NUM
 
+extern void vTaskEnterCritical(portMUX_TYPE *mux);
+extern void vTaskExitCritical(portMUX_TYPE *mux);
+
 #ifdef __cplusplus
 }
 #endif