From cebdade610264343fe275ca3bb2a811c8d34c505 Mon Sep 17 00:00:00 2001
From: Rahix <rahix@rahix.de>
Date: Fri, 19 Jul 2019 18:23:15 +0200
Subject: [PATCH] feat(streams): Add descriptor table lock
Signed-off-by: Rahix <rahix@rahix.de>
---
epicardium/modules/stream.c | 32 ++++++++++++++++++++++++++++++++
epicardium/modules/stream.h | 3 +++
2 files changed, 35 insertions(+)
diff --git a/epicardium/modules/stream.c b/epicardium/modules/stream.c
index 561c398a..b39e0c1d 100644
--- a/epicardium/modules/stream.c
+++ b/epicardium/modules/stream.c
@@ -1,18 +1,32 @@
#include <string.h>
+#include "FreeRTOS.h"
+#include "semphr.h"
+
#include "epicardium.h"
#include "stream.h"
+/* Internal buffer of registered streams */
static struct stream_info *stream_table[SD_MAX];
+/* Lock for modifying the stream info table */
+static StaticSemaphore_t stream_table_lock_data;
+static SemaphoreHandle_t stream_table_lock;
+
int stream_init()
{
memset(stream_table, 0x00, sizeof(stream_table));
+ stream_table_lock =
+ xSemaphoreCreateMutexStatic(&stream_table_lock_data);
return 0;
}
int stream_register(int sd, struct stream_info *stream)
{
+ if (xSemaphoreTake(stream_table_lock, STREAM_MUTEX_WAIT) != pdTRUE) {
+ return -EBUSY;
+ }
+
if (sd < 0 || sd >= SD_MAX) {
return -EINVAL;
}
@@ -23,11 +37,17 @@ int stream_register(int sd, struct stream_info *stream)
}
stream_table[sd] = stream;
+
+ xSemaphoreGive(stream_table_lock);
return 0;
}
int stream_deregister(int sd, struct stream_info *stream)
{
+ if (xSemaphoreTake(stream_table_lock, STREAM_MUTEX_WAIT) != pdTRUE) {
+ return -EBUSY;
+ }
+
if (sd < 0 || sd >= SD_MAX) {
return -EINVAL;
}
@@ -38,11 +58,22 @@ int stream_deregister(int sd, struct stream_info *stream)
}
stream_table[sd] = NULL;
+
+ xSemaphoreGive(stream_table_lock);
return 0;
}
int epic_stream_read(int sd, void *buf, size_t count)
{
+ /*
+ * TODO: In theory, multiple reads on different streams can happen
+ * simulaneously. I don't know what the most efficient implementation
+ * of this would look like.
+ */
+ if (xSemaphoreTake(stream_table_lock, STREAM_MUTEX_WAIT) != pdTRUE) {
+ return -EBUSY;
+ }
+
if (sd < 0 || sd >= SD_MAX) {
return -EBADF;
}
@@ -72,5 +103,6 @@ int epic_stream_read(int sd, void *buf, size_t count)
}
}
+ xSemaphoreGive(stream_table_lock);
return i / stream->item_size;
}
diff --git a/epicardium/modules/stream.h b/epicardium/modules/stream.h
index 622aee40..5bce8d56 100644
--- a/epicardium/modules/stream.h
+++ b/epicardium/modules/stream.h
@@ -7,6 +7,9 @@
#include "FreeRTOS.h"
#include "queue.h"
+/* Time to wait for the descriptor table lock to become available */
+#define STREAM_MUTEX_WAIT pdMS_TO_TICKS(100)
+
/**
* **Stream Descriptors**:
*
--
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