Add SMP template port and example (#900)

* Add SMP template port and example
* Add readme file for smp configuration
* Update SMP build flow and add CI build

---------

Co-authored-by: Soren Ptak <ptaksoren@gmail.com>
Co-authored-by: Rahul Kar <118818625+kar-rahul-aws@users.noreply.github.com>

.github/workflows/kernel-demos.yml

@@ -111,6 +111,13 @@ jobs:
           cmake -S . -B build
           cmake --build build
 
+      - name: Build CMake SMP Example Demo
+        shell: bash
+        working-directory: examples/cmake_example
+        run: |
+          cmake -S . -B build -DFREERTOS_SMP_EXAMPLE=1
+          cmake --build build
+
   MSP430-GCC:
     name: GNU MSP430 Toolchain
     runs-on: ubuntu-latest

examples/cmake_example/CMakeLists.txt

@@ -7,10 +7,19 @@ set(FREERTOS_KERNEL_PATH "../../")
 # Add the freertos_config for FreeRTOS-Kernel
 add_library(freertos_config INTERFACE)
 
-target_include_directories(freertos_config
-    INTERFACE
-    ../sample_configuration
-)
+if (DEFINED FREERTOS_SMP_EXAMPLE AND FREERTOS_SMP_EXAMPLE STREQUAL "1")
+    message(STATUS "Build FreeRTOS SMP example")
+    target_include_directories(freertos_config
+        INTERFACE
+        "../sample_configuration/smp"
+    )
+else()
+    message(STATUS "Build FreeRTOS example")
+    target_include_directories(freertos_config
+        INTERFACE
+        "../sample_configuration"
+    )
+endif()
 
 # Select the heap port.  values between 1-4 will pick a heap.
 set(FREERTOS_HEAP "4" CACHE STRING "" FORCE)

examples/sample_configuration/smp/FreeRTOSConfig.h

@@ -0,0 +1,65 @@
+/*
+ * FreeRTOS Kernel <DEVELOPMENT BRANCH>
+ * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
+ */
+
+/*******************************************************************************
+ * This file provides an example FreeRTOSConfig.h header file, inclusive of an
+ * abbreviated explanation of each configuration item.  Online and reference
+ * documentation provides more information.
+ * https://www.freertos.org/a00110.html
+ *
+ * Constant values enclosed in square brackets ('[' and ']') must be completed
+ * before this file will build.
+ *
+ * Use the FreeRTOSConfig.h supplied with the RTOS port in use rather than this
+ * generic file, if one is available.
+ ******************************************************************************/
+
+#ifndef __FREERTOS_CONFIG_SMP_H__
+#define __FREERTOS_CONFIG_SMP_H__
+
+#include "../FreeRTOSConfig.h"
+
+/******************************************************************************/
+/* Scheduling behaviour related definitions. **********************************/
+/******************************************************************************/
+
+/* Set configNUMBER_OF_CORES to greater than 1 to enable running one instance of
+ * FreeRTOS kernel to schedule tasks across multiple identical processor cores. */
+#define configNUMBER_OF_CORES    2
+
+/******************************************************************************/
+/* Hook and callback function related definitions. ****************************/
+/******************************************************************************/
+
+/* Set the following configUSE_* constants to 1 to include the named hook
+ * functionality in the build.  Set to 0 to exclude the hook functionality from the
+ * build.  The application writer is responsible for providing the hook function
+ * for any set to 1.  See https://www.freertos.org/a00016.html */
+#define configUSE_PASSIVE_IDLE_HOOK    0
+
+#endif /* __FREERTOS_CONFIG_SMP_H__ */

examples/sample_configuration/smp/readme.md

@@ -0,0 +1,10 @@
+# Configuration support for FreeRTOS SMP
+
+## Overview
+The FreeRTOSConfig.h provided in this folder is a sample configuration that will
+assist you in preparing the configuration to enable SMP support in the FreeRTOS
+Kernel for your application.
+
+Based on single core sample configuration file, this configuration file is created
+with minimal configuration change. More SMP scheduler configurations can be found
+in [Symmetric Multiprocessing (SMP) with FreeRTOS](https://freertos.org/symmetric-multiprocessing-introduction.html)

portable/template/port.c

@@ -25,8 +25,18 @@ StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
 void vPortYield( void )
 {
     /* Save the current Context */
+
     /* Switch to the highest priority task that is ready to run. */
-    vTaskSwitchContext();
+    #if ( configNUMBER_OF_CORES == 1 )
+    {
+        vTaskSwitchContext();
+    }
+    #else
+    {
+        vTaskSwitchContext( portGET_CORE_ID() );
+    }
+    #endif
+
     /* Start executing the task we have just switched to. */
 }
 
@@ -35,12 +45,34 @@ static void prvTickISR( void )
     /* Interrupts must have been enabled for the ISR to fire, so we have to
      * save the context with interrupts enabled. */
 
-    /* Maintain the tick count. */
-    if( xTaskIncrementTick() != pdFALSE )
+    #if ( configNUMBER_OF_CORES == 1 )
     {
-        /* Switch to the highest priority task that is ready to run. */
-        vTaskSwitchContext();
+        /* Maintain the tick count. */
+        if( xTaskIncrementTick() != pdFALSE )
+        {
+            /* Switch to the highest priority task that is ready to run. */
+            vTaskSwitchContext();
+        }
     }
+    #else
+    {
+        UBaseType_t ulPreviousMask;
+
+        /* Tasks or ISRs running on other cores may still in critical section in
+         * multiple cores environment. Incrementing tick needs to performed in
+         * critical section. */
+        ulPreviousMask = taskENTER_CRITICAL_FROM_ISR();
+
+        /* Maintain the tick count. */
+        if( xTaskIncrementTick() != pdFALSE )
+        {
+            /* Switch to the highest priority task that is ready to run. */
+            vTaskSwitchContext( portGET_CORE_ID() );
+        }
+
+        taskEXIT_CRITICAL_FROM_ISR( ulPreviousMask );
+    }
+    #endif /* if ( configNUMBER_OF_CORES == 1 ) */
 
     /* start executing the new task */
 }

portable/template/portmacro.h

@@ -64,26 +64,42 @@ typedef unsigned char    UBaseType_t;
 /*-----------------------------------------------------------*/
 
     #define portGET_HIGHEST_PRIORITY( uxTopPriority, uxReadyPriorities ) \
-    {                                                                    \
+    do {                                                                 \
         uxTopPriority = 0;                                               \
-    }                                                                    \
-    while( 0 )
+    } while( 0 )
 
 #endif /* configUSE_PORT_OPTIMISED_TASK_SELECTION */
 
-#define portDISABLE_INTERRUPTS()   \
-    { /* Disable the interrupts */ \
-    }
-#define portENABLE_INTERRUPTS()   \
-    { /* Enable the interrupts */ \
-    }
+/* Disable the interrupts */
+#define portDISABLE_INTERRUPTS()    do {} while( 0 )
 
-#define portENTER_CRITICAL()                                             \
-    { /* preserve current interrupt state and then disable interrupts */ \
-    }
-#define portEXIT_CRITICAL()                              \
-    { /* restore previously preserved interrupt state */ \
-    }
+/* Enable the interrupts */
+#define portENABLE_INTERRUPTS()     do {} while( 0 )
+
+#if ( configNUMBER_OF_CORES == 1 )
+/* preserve current interrupt state and then disable interrupts */
+    #define portENTER_CRITICAL()    do {} while( 0 )
+
+/* restore previously preserved interrupt state */
+    #define portEXIT_CRITICAL()     do {} while( 0 )
+#else
+
+/* The port can maintain the critical nesting count in TCB or maintain the critical
+ * nesting count in the port. */
+    #define portCRITICAL_NESTING_IN_TCB    1
+
+/* vTaskEnterCritical and vTaskExitCritical should be used in the implementation
+ * of portENTER/EXIT_CRITICAL if the number of cores is more than 1 in the system. */
+    #define portENTER_CRITICAL             vTaskEnterCritical
+    #define portEXIT_CRITICAL              vTaskExitCritical
+
+/* vTaskEnterCriticalFromISR and vTaskExitCriticalFromISR should be used in the
+ * implementation of portENTER/EXIT_CRITICAL_FROM_ISR if the number of cores is
+ * more than 1 in the system. */
+    #define portENTER_CRITICAL_FROM_ISR    vTaskEnterCriticalFromISR
+    #define portEXIT_CRITICAL_FROM_ISR     vTaskExitCriticalFromISR
+
+#endif /* if ( configNUMBER_OF_CORES == 1 ) */
 
 extern void vPortYield( void );
 #define portYIELD()                                           vPortYield()
@@ -92,4 +108,35 @@ extern void vPortYield( void );
 #define portTASK_FUNCTION_PROTO( vFunction, pvParameters )    void vFunction( void * pvParameters )
 #define portTASK_FUNCTION( vFunction, pvParameters )          void vFunction( void * pvParameters )
 
+#if ( configNUMBER_OF_CORES > 1 )
+    /* Return the core ID on which the code is running. */
+    #define portGET_CORE_ID()                0
+
+/* Set the interrupt mask. */
+    #define portSET_INTERRUPT_MASK()         0
+
+/* Clear the interrupt mask. */
+    #define portCLEAR_INTERRUPT_MASK( x )    ( ( void ) ( x ) )
+
+/* Request the core ID x to yield. */
+    #define portYIELD_CORE( x )              do {} while( 0 )
+
+/* Acquire the TASK lock. TASK lock is a recursive lock.
+ * It should be able to be locked by the same core multiple times. */
+    #define portGET_TASK_LOCK()              do {} while( 0 )
+
+/* Release the TASK lock. If a TASK lock is locked by the same core multiple times,
+ * it should be released as many times as it is locked. */
+    #define portRELEASE_TASK_LOCK()          do {} while( 0 )
+
+/* Acquire the ISR lock. ISR lock is a recursive lock.
+ * It should be able to be locked by the same core multiple times. */
+    #define portGET_ISR_LOCK()               do {} while( 0 )
+
+/* Release the ISR lock. If a ISR lock is locked by the same core multiple times, \
+ * it should be released as many times as it is locked. */
+    #define portRELEASE_ISR_LOCK()           do {} while( 0 )
+
+#endif /* if ( configNUMBER_OF_CORES > 1 ) */
+
 #endif /* PORTMACRO_H */