FreeRTOS posix port hangs when issuing interrupt-safe calls from an external thread

[doppioandante]

FreeRTOS: version: v11.1.0 FreeRTOS port: FreeRTOS Posix port OS: Ubuntu 22.04

I'm using the freertos posix port to test a the firmware logic without the need for a hardware. The real hardware receives data via an interrupt, which is then pushed on a queue like:

xQueueSendFromISR(..., &waked)
portYIELD_FROM_ISR(waked);

On the simulator I'm using an external thread (pthread) not managed by FreeRTOS that wait for events on a local network interface; when an event comes, the same code is called, but I've found that it makes FreeRTOS hang or even assert often.

I also added the following assert to vPortExitCritical, and it somestimes get triggered, suggesting me that either there's something wrong in the port or, more probably, I'm invalidating the invariant by using the API incorrectly:

void vPortExitCritical( void )
{
    uxCriticalNesting--;
    configASSERT(uxCriticalNesting >= 0);

    /* If we have reached 0 then re-enable the interrupts. */
    if( uxCriticalNesting == 0 )
    {
        vPortEnableInterrupts();
    }
}

(BTW, wouldn't a mutex or at least an atomic increment/decrement be needed for uxCriticalNesting?)

I stripped down the pattern that makes my code crash down to:

#define _GNU_SOURCE

#include <FreeRTOS.h>
#include <task.h>
#include <queue.h>

#include <stdio.h>
#include <stdbool.h>
#include <pthread.h>
#include <unistd.h>
#include <signal.h>

static void init_globals();
static void init_tasks();

static void reader_task(void*);
static void periodic_task(void*);
static void* interrupt_simulator(void*);

static void send_int(int value);

static QueueHandle_t queue;

int main() {
    init_globals();
    init_tasks();

    vTaskStartScheduler();
    return 0;
}

void init_globals() {
    queue = xQueueCreate(128, sizeof(int));
}

void init_tasks() {
    xTaskCreate(reader_task, "ReaderTask", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(periodic_task, "PeriodicTask", configMINIMAL_STACK_SIZE, NULL, 2, NULL);

    pthread_t tid;
    sigset_t set;
    pthread_attr_t attr;

    sigfillset(&set);
    pthread_attr_init(&attr);
    pthread_attr_setsigmask_np(&attr, &set);

    pthread_create(&tid, &attr, interrupt_simulator, NULL);
}

void reader_task(void* args) {
    (void) args;

    while (true) {
        int val;
        xQueueReceive(queue, &val, portMAX_DELAY);

        send_int(val+1);
    }
}

void periodic_task(void* args) {
    (void) args;

    TickType_t previousWakeTime = xTaskGetTickCount();

    while (true) {
        send_int(0);

        xTaskDelayUntil(&previousWakeTime, pdMS_TO_TICKS(100));
    }
}

static void send_int(int val)
{
    taskENTER_CRITICAL();
    printf("%d\n", val);
    taskEXIT_CRITICAL();
}

static void* interrupt_simulator(void* args)
{
    (void) args;
    int val = 1;
    BaseType_t waked = pdFALSE;

    while (true) {
        usleep(1000);

        xQueueSendFromISR(queue, &val, &waked);
        portYIELD_FROM_ISR(waked);

        val += 1;
    }

    return NULL;
}

freertos_posix_impl.c

```c #include #include #include #include /* FreeRTOS kernel includes. */ #include "FreeRTOS.h" #include "task.h" /* * Prototypes for the standard FreeRTOS application hook (callback) functions * implemented within this file. See http://www.freertos.org/a00016.html . */ void vApplicationMallocFailedHook( void ); void vApplicationIdleHook( void ); void vApplicationStackOverflowHook( TaskHandle_t pxTask, char * pcTaskName ); void vApplicationTickHook( void ); void vApplicationGetIdleTaskMemory( StaticTask_t ** ppxIdleTaskTCBBuffer, StackType_t ** ppxIdleTaskStackBuffer, uint32_t * pulIdleTaskStackSize ); void vApplicationGetTimerTaskMemory( StaticTask_t ** ppxTimerTaskTCBBuffer, StackType_t ** ppxTimerTaskStackBuffer, uint32_t * pulTimerTaskStackSize ); /* When configSUPPORT_STATIC_ALLOCATION is set to 1 the application writer can * use a callback function to optionally provide the memory required by the idle * and timer tasks. This is the stack that will be used by the timer task. It is * declared here, as a global, so it can be checked by a test that is implemented * in a different file. */ StackType_t uxTimerTaskStack[ configTIMER_TASK_STACK_DEPTH ]; /*-----------------------------------------------------------*/ void vApplicationMallocFailedHook( void ) { /* vApplicationMallocFailedHook() will only be called if * configUSE_MALLOC_FAILED_HOOK is set to 1 in FreeRTOSConfig.h. It is a hook * function that will get called if a call to pvPortMalloc() fails. * pvPortMalloc() is called internally by the kernel whenever a task, queue, * timer or semaphore is created. It is also called by various parts of the * demo application. If heap_1.c, heap_2.c or heap_4.c is being used, then the * size of the heap available to pvPortMalloc() is defined by * configTOTAL_HEAP_SIZE in FreeRTOSConfig.h, and the xPortGetFreeHeapSize() * API function can be used to query the size of free heap space that remains * (although it does not provide information on how the remaining heap might be * fragmented). See http://www.freertos.org/a00111.html for more * information. */ vAssertCalled( __FILE__, __LINE__ ); } /*-----------------------------------------------------------*/ void vApplicationIdleHook( void ) { /* vApplicationIdleHook() will only be called if configUSE_IDLE_HOOK is set * to 1 in FreeRTOSConfig.h. It will be called on each iteration of the idle * task. It is essential that code added to this hook function never attempts * to block in any way (for example, call xQueueReceive() with a block time * specified, or call vTaskDelay()). If application tasks make use of the * vTaskDelete() API function to delete themselves then it is also important * that vApplicationIdleHook() is permitted to return to its calling function, * because it is the responsibility of the idle task to clean up memory * allocated by the kernel to any task that has since deleted itself. */ usleep( 15000 ); } /*-----------------------------------------------------------*/ void vApplicationStackOverflowHook( TaskHandle_t pxTask, char * pcTaskName ) { ( void ) pcTaskName; ( void ) pxTask; /* Run time stack overflow checking is performed if * configCHECK_FOR_STACK_OVERFLOW is defined to 1 or 2. This hook * function is called if a stack overflow is detected. This function is * provided as an example only as stack overflow checking does not function * when running the FreeRTOS POSIX port. */ vAssertCalled( __FILE__, __LINE__ ); } /*-----------------------------------------------------------*/ void vApplicationTickHook( void ) { /* This function will be called by each tick interrupt if * configUSE_TICK_HOOK is set to 1 in FreeRTOSConfig.h. User code can be * added here, but the tick hook is called from an interrupt context, so * code must not attempt to block, and only the interrupt safe FreeRTOS API * functions can be used (those that end in FromISR()). */ } void vLoggingPrintf( const char * pcFormat, ... ) { va_list arg; va_start( arg, pcFormat ); vprintf( pcFormat, arg ); va_end( arg ); } /*-----------------------------------------------------------*/ void vApplicationDaemonTaskStartupHook( void ) { /* This function will be called once only, when the daemon task starts to * execute (sometimes called the timer task). This is useful if the * application includes initialisation code that would benefit from executing * after the scheduler has been started. */ } /*-----------------------------------------------------------*/ void vAssertCalled( const char * const pcFileName, unsigned long ulLine ) { volatile uint32_t ulSetToNonZeroInDebuggerToContinue = 0; /* Called if an assertion passed to configASSERT() fails. See * https://www.FreeRTOS.org/a00110.html#configASSERT for more information. */ /* Parameters are not used. */ ( void ) ulLine; ( void ) pcFileName; taskENTER_CRITICAL(); { printf("Assert failed: %s at line %ld\n", pcFileName, ulLine); /* You can step out of this function to debug the assertion by using * the debugger to set ulSetToNonZeroInDebuggerToContinue to a non-zero * value. */ while( ulSetToNonZeroInDebuggerToContinue == 0 ) { __asm volatile ( "NOP" ); __asm volatile ( "NOP" ); } } taskEXIT_CRITICAL(); } /*-----------------------------------------------------------*/ /* configUSE_STATIC_ALLOCATION is set to 1, so the application must provide an * implementation of vApplicationGetIdleTaskMemory() to provide the memory that is * used by the Idle task. */ void vApplicationGetIdleTaskMemory( StaticTask_t ** ppxIdleTaskTCBBuffer, StackType_t ** ppxIdleTaskStackBuffer, uint32_t * pulIdleTaskStackSize ) { /* If the buffers to be provided to the Idle task are declared inside this * function then they must be declared static - otherwise they will be allocated on * the stack and so not exists after this function exits. */ static StaticTask_t xIdleTaskTCB; static StackType_t uxIdleTaskStack[ configMINIMAL_STACK_SIZE ]; /* Pass out a pointer to the StaticTask_t structure in which the Idle task's * state will be stored. */ *ppxIdleTaskTCBBuffer = &xIdleTaskTCB; /* Pass out the array that will be used as the Idle task's stack. */ *ppxIdleTaskStackBuffer = uxIdleTaskStack; /* Pass out the size of the array pointed to by *ppxIdleTaskStackBuffer. * Note that, as the array is necessarily of type StackType_t, * configMINIMAL_STACK_SIZE is specified in words, not bytes. */ *pulIdleTaskStackSize = configMINIMAL_STACK_SIZE; } /*-----------------------------------------------------------*/ /* configUSE_STATIC_ALLOCATION and configUSE_TIMERS are both set to 1, so the * application must provide an implementation of vApplicationGetTimerTaskMemory() * to provide the memory that is used by the Timer service task. */ void vApplicationGetTimerTaskMemory( StaticTask_t ** ppxTimerTaskTCBBuffer, StackType_t ** ppxTimerTaskStackBuffer, uint32_t * pulTimerTaskStackSize ) { /* If the buffers to be provided to the Timer task are declared inside this * function then they must be declared static - otherwise they will be allocated on * the stack and so not exists after this function exits. */ static StaticTask_t xTimerTaskTCB; /* Pass out a pointer to the StaticTask_t structure in which the Timer * task's state will be stored. */ *ppxTimerTaskTCBBuffer = &xTimerTaskTCB; /* Pass out the array that will be used as the Timer task's stack. */ *ppxTimerTaskStackBuffer = uxTimerTaskStack; /* Pass out the size of the array pointed to by *ppxTimerTaskStackBuffer. * Note that, as the array is necessarily of type StackType_t, * configMINIMAL_STACK_SIZE is specified in words, not bytes. */ *pulTimerTaskStackSize = configTIMER_TASK_STACK_DEPTH; } #undef traceMOVED_TASK_TO_DELAYED_LIST #define traceMOVED_TASK_TO_DELAYED_LIST() printf("%ld\n", pxCurrentTCB->uxTCBNumber); ```

FreeRTOSConfig.h

```C /* * FreeRTOS V202212.00 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * 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 * */ #ifndef FREERTOS_CONFIG_H #define FREERTOS_CONFIG_H /*----------------------------------------------------------- * Application specific definitions. * * These definitions should be adjusted for your particular hardware and * application requirements. * * THESE PARAMETERS ARE DESCRIBED WITHIN THE 'CONFIGURATION' SECTION OF THE * FreeRTOS API DOCUMENTATION AVAILABLE ON THE FreeRTOS.org WEB SITE. See * https://www.FreeRTOS.org/a00110.html *----------------------------------------------------------*/ #define configUSE_PREEMPTION 1 #define configUSE_PORT_OPTIMISED_TASK_SELECTION 0 #define configUSE_IDLE_HOOK 1 #define configUSE_TICK_HOOK 1 #define configUSE_DAEMON_TASK_STARTUP_HOOK 1 #define configTICK_RATE_HZ ( 10000 ) /* In this non-real time simulated environment the tick frequency has to be at least a multiple of the Win32 tick frequency, and therefore very slow. */ #define configMINIMAL_STACK_SIZE ( ( unsigned short ) PTHREAD_STACK_MIN ) /* The stack size being passed is equal to the minimum stack size needed by pthread_create(). */ #define configTOTAL_HEAP_SIZE ( ( size_t ) ( configMINIMAL_STACK_SIZE * 1000 ) ) #define configMAX_TASK_NAME_LEN ( 12 ) #define configUSE_TRACE_FACILITY 1 #define configUSE_16_BIT_TICKS 0 #define configIDLE_SHOULD_YIELD 1 #define configUSE_MUTEXES 1 #define configCHECK_FOR_STACK_OVERFLOW 1 #define configUSE_RECURSIVE_MUTEXES 1 #define configQUEUE_REGISTRY_SIZE 20 #define configUSE_APPLICATION_TASK_TAG 1 #define configUSE_COUNTING_SEMAPHORES 1 #define configUSE_ALTERNATIVE_API 0 #define configUSE_QUEUE_SETS 1 #define configUSE_TASK_NOTIFICATIONS 1 #define configSUPPORT_STATIC_ALLOCATION 1 /* Software timer related configuration options. The maximum possible task * priority is configMAX_PRIORITIES - 1. The priority of the timer task is * deliberately set higher to ensure it is correctly capped back to * configMAX_PRIORITIES - 1. */ #define configUSE_TIMERS 1 #define configTIMER_TASK_PRIORITY ( configMAX_PRIORITIES - 1 ) #define configTIMER_QUEUE_LENGTH 20 #define configTIMER_TASK_STACK_DEPTH ( configMINIMAL_STACK_SIZE * 2 ) #define configMAX_PRIORITIES ( 12 ) /* Run time stats gathering configuration options. */ unsigned long ulGetRunTimeCounterValue( void ); /* Prototype of function that returns run time counter. */ void vConfigureTimerForRunTimeStats( void ); /* Prototype of function that initialises the run time counter. */ #define configGENERATE_RUN_TIME_STATS 1 /* This demo can use of one or more example stats formatting functions. These * format the raw data provided by the uxTaskGetSystemState() function in to human * readable ASCII form. See the notes in the implementation of vTaskList() within * FreeRTOS/Source/tasks.c for limitations. */ #define configUSE_STATS_FORMATTING_FUNCTIONS 0 /* Enables the test whereby a stack larger than the total heap size is * requested. */ #define configSTACK_DEPTH_TYPE uint32_t /* Set the following definitions to 1 to include the API function, or zero * to exclude the API function. In most cases the linker will remove unused * functions anyway. */ #define INCLUDE_vTaskPrioritySet 1 #define INCLUDE_uxTaskPriorityGet 1 #define INCLUDE_vTaskDelete 1 #define INCLUDE_vTaskCleanUpResources 0 #define INCLUDE_vTaskSuspend 1 #define INCLUDE_vTaskDelayUntil 1 #define INCLUDE_vTaskDelay 1 #define INCLUDE_uxTaskGetStackHighWaterMark 1 #define INCLUDE_uxTaskGetStackHighWaterMark2 1 #define INCLUDE_xTaskGetSchedulerState 1 #define INCLUDE_xTimerGetTimerDaemonTaskHandle 1 #define INCLUDE_xTaskGetIdleTaskHandle 1 #define INCLUDE_xTaskGetHandle 1 #define INCLUDE_eTaskGetState 1 #define INCLUDE_xSemaphoreGetMutexHolder 1 #define INCLUDE_xTimerPendFunctionCall 1 #define INCLUDE_xTaskAbortDelay 1 #define configINCLUDE_MESSAGE_BUFFER_AMP_DEMO 0 #if ( configINCLUDE_MESSAGE_BUFFER_AMP_DEMO == 1 ) extern void vGenerateCoreBInterrupt( void * xUpdatedMessageBuffer ); #define sbSEND_COMPLETED( pxStreamBuffer ) vGenerateCoreBInterrupt( pxStreamBuffer ) #endif /* configINCLUDE_MESSAGE_BUFFER_AMP_DEMO */ extern void vAssertCalled( const char * const pcFileName, unsigned long ulLine ); /* projCOVERAGE_TEST should be defined on the command line so this file can be * used with multiple project configurations. If it is */ #ifndef projCOVERAGE_TEST #error projCOVERAGE_TEST should be defined to 1 or 0 on the command line. #endif #if ( projCOVERAGE_TEST == 1 ) /* Insert NOPs in empty decision paths to ensure both true and false paths * are being tested. */ #define mtCOVERAGE_TEST_MARKER() __asm volatile ( "NOP" ) /* Ensure the tick count overflows during the coverage test. */ #define configINITIAL_TICK_COUNT 0xffffd800UL /* Allows tests of trying to allocate more than the heap has free. */ #define configUSE_MALLOC_FAILED_HOOK 0 /* To test builds that remove the static qualifier for debug builds. */ #define portREMOVE_STATIC_QUALIFIER #else /* if ( projCOVERAGE_TEST == 1 ) */ /* It is a good idea to define configASSERT() while developing. configASSERT() * uses the same semantics as the standard C assert() macro. Don't define * configASSERT() when performing code coverage tests though, as it is not * intended to asserts() to fail, some some code is intended not to run if no * errors are present. */ #define configASSERT( x ) if( ( x ) == 0 ) vAssertCalled( __FILE__, __LINE__ ) #define configUSE_MALLOC_FAILED_HOOK 1 /* Include the FreeRTOS+Trace FreeRTOS trace macro definitions. */ // #include "trcRecorder.h" #endif /* if ( projCOVERAGE_TEST == 1 ) */ /* networking definitions */ #define configMAC_ISR_SIMULATOR_PRIORITY ( configMAX_PRIORITIES - 1 ) /* Prototype for the function used to print out. In this case it prints to the * console before the network is connected then a UDP port after the network has * connected. */ extern void vLoggingPrintf( const char * pcFormatString, ... ); /* Set to 1 to print out debug messages. If ipconfigHAS_DEBUG_PRINTF is set to * 1 then FreeRTOS_debug_printf should be defined to the function used to print * out the debugging messages. */ #define ipconfigHAS_DEBUG_PRINTF 1 #if ( ipconfigHAS_DEBUG_PRINTF == 1 ) #define FreeRTOS_debug_printf( X ) vLoggingPrintf X #endif /* Set to 1 to print out non debugging messages, for example the output of the * FreeRTOS_netstat() command, and ping replies. If ipconfigHAS_PRINTF is set to 1 * then FreeRTOS_printf should be set to the function used to print out the * messages. */ #define ipconfigHAS_PRINTF 0 #if ( ipconfigHAS_PRINTF == 1 ) #define FreeRTOS_printf( X ) vLoggingPrintf X #endif #endif /* FREERTOS_CONFIG_H */ ```

[paulbartell]

@doppioandante Consider using the event api defined in wait_for_event.c to simulate your interrupt.

[shubnil]

@doppioandante Please update your observations after using "wait_for_event.c".

[doppioandante]

I'm not quite sure how I could use that API, it seems to me like an internal implementation detail of the POSIX port. An "simulated interrupt" mimicking the hardware counterpart would interrupt the current task, do its things and then yield back to freertos, right? While the wait_for_event API looks like it is designed to wait for on a condition, and it's indeed used by the port to resume tasks.