[iot/goam] Fixed SPIFFS read/write race condition

1 files changed, 33 insertions, 0 deletions

diff --git a/Year 3/Internet of things/goam/main/spiffs.c b/Year 3/Internet of things/goam/main/spiffs.c
index 61e1776..1e37525 100644
--- a/Year 3/Internet of things/goam/main/spiffs.c
+++ b/Year 3/Internet of things/goam/main/spiffs.c
@@ -3,6 +3,7 @@
 #include <fcntl.h>
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
+#include "freertos/semphr.h"
 #include "esp_log.h"
 #include "esp_spiffs.h"
 
@@ -14,6 +15,8 @@ static const char *TAG = "example";
  * Public interface
  */
 
+static SemaphoreHandle_t rw_mutex = NULL;
+
 void spiffs_init() {
 	esp_vfs_spiffs_conf_t conf = {
 		.base_path              = SPIFFS_PREFIX,
@@ -53,12 +56,22 @@ void spiffs_init() {
 			ESP_LOGI(TAG, "SPIFFS_check() successful");
 		}
 	}
+
+	rw_mutex = xSemaphoreCreateMutex();
+	if (rw_mutex == NULL) {
+		ESP_LOGE(TAG, "Couldn't create Read/Write mutex, SPIFFS operations will crash");
+	}
 }
 
 void spiffs_write(const char* filename, const char* data, int data_len) {
+	if (xSemaphoreTake(rw_mutex, 100) == pdFALSE) {
+		return;
+	}
+
 	int outf = open(filename, O_WRONLY | O_CREAT | O_TRUNC);
 	if (outf < 0) {
 		ESP_LOGE(TAG, "Couldn't open file \"%s\" for writing!", filename);
+		xSemaphoreGive(rw_mutex);
 		return;
 	}
 
@@ -76,12 +89,28 @@ void spiffs_write(const char* filename, const char* data, int data_len) {
 	else {
 		ESP_LOGD(TAG, "Wrote %d bytes from \"%s\"", length, filename);
 	}
+	xSemaphoreGive(rw_mutex);
 }
 
+static int readers = 0;
+
 int spiffs_read(const char* filename, char** data) {
+	if (readers == 0) {
+		if (xSemaphoreTake(rw_mutex, 100) == pdTRUE) {
+			vTaskDelay(150 / portTICK_PERIOD_MS);
+		}
+		else {
+			*data = NULL;
+			return 0;
+		}
+	}
+	readers++;
+
 	int inf = open(filename, O_RDONLY);
 	if (inf < 0) {
 		ESP_LOGW(TAG, "Couldn't read from file \"%s\"!", filename);
+		readers--;
+		if (readers == 0) xSemaphoreGive(rw_mutex);
 		return 0;
 	}
 
@@ -89,6 +118,8 @@ int spiffs_read(const char* filename, char** data) {
 	if (fstat(inf, &buf) < 0) {
 		close(inf);
 		ESP_LOGE(TAG, "Couldn't read stat of file \"%s\"!", filename);
+		readers--;
+		if (readers == 0) xSemaphoreGive(rw_mutex);
 		return 0;
 	}
 
@@ -98,5 +129,7 @@ int spiffs_read(const char* filename, char** data) {
 
 	close(inf);
 	ESP_LOGD(TAG, "read %d bytes from \"%s\"", length, filename);
+	readers--;
+	if (readers == 0) xSemaphoreGive(rw_mutex);
 	return length;
 }