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modbus: Exit server task gracefully to correctly cleanup lwip internals

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Current lwip implementation does not support deleting a task which is
actively waiting on `select()` or `poll()` API.
Therefore we have to make sure that `select()` exits to deallocate its internal
callback before deleting the task. This is achieved by a shutdown
semaphore which informs the client once the `select()` exitted.

fix slave
This commit is contained in:
David Cermak 2021-01-20 09:19:49 +01:00 committed by bot
parent 890ee19ee4
commit 898cac0061
1 changed files with 21 additions and 1 deletions
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22
components/freemodbus/tcp_slave/port/port_tcp_slave.c
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@ -66,6 +66,7 @@ void vMBPortEventClose( void );
/* ----------------------- Static variables ---------------------------------*/
static int xListenSock = -1;
static SemaphoreHandle_t xShutdownSemaphore = NULL;
static MbSlavePortConfig_t xConfig = { 0 };
/* ----------------------- Static functions ---------------------------------*/
@ -462,6 +463,11 @@ static void vMBTCPPortServerTask(void *pvParameters)
// Wait for an activity on one of the sockets, timeout is NULL, so wait indefinitely
xErr = select(xMaxSd + 1 , &xReadSet , NULL , NULL , NULL);
if ((xErr < 0) && (errno != EINTR)) {
// First check if the task is not flagged for shutdown
if (xListenSock == -1 && xShutdownSemaphore) {
xSemaphoreGive(xShutdownSemaphore);
vTaskDelete(NULL);
}
// error occurred during wait for read
ESP_LOGE(MB_TCP_SLAVE_PORT_TAG, "select() errno = %d.", errno);
continue;
@ -626,8 +632,22 @@ void
vMBTCPPortClose( )
{
// Release resources for the event queue.
// Try to exit the task gracefully, so select could release its internal callbacks
// that were allocated on the stack of the task we're going to delete
xShutdownSemaphore = xSemaphoreCreateBinary();
vTaskResume(xConfig.xMbTcpTaskHandle);
if (xShutdownSemaphore == NULL || // if no semaphore (alloc issues) or couldn't acquire it, just delete the task
xSemaphoreTake(xShutdownSemaphore, 2*pdMS_TO_TICKS(CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND)) != pdTRUE) {
ESP_LOGE(MB_TCP_SLAVE_PORT_TAG, "Task couldn't exit gracefully within timeout -> abruptly deleting the task");
vTaskDelete(xConfig.xMbTcpTaskHandle);
}
if (xShutdownSemaphore) {
vSemaphoreDelete(xShutdownSemaphore);
xShutdownSemaphore = NULL;
}
vMBPortEventClose( );
vTaskDelete(xConfig.xMbTcpTaskHandle);
}
void