0006-tty-n_r3964-for-tx_blocks-use-a-real-kernel-list.patch

From 55124901b0e4b05999669830cf6e0b240f8cb2fd Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Thu, 24 Jan 2019 13:35:36 +0100
Subject: [PATCH 06/15] tty: n_r3964: for tx_blocks, use a real kernel list

The tx blocks have a hand-rolled linked list structure, use a "normal"
kernel list structure instead, making the code smaller and easier to
understand and verify that it really does what we think it should be
doing.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_r3964.c |   85 +++++++++++++++-----------------------------------
 1 file changed, 26 insertions(+), 59 deletions(-)

--- a/drivers/tty/n_r3964.c
+++ b/drivers/tty/n_r3964.c
@@ -140,7 +140,7 @@ struct rx_block_header {
 struct tx_block_header {
 	unsigned int length;	/* length in chars without header */
 	unsigned char *data;
-	struct tx_block_header *next;
+	struct list_head node;
 	struct r3964_client_info *owner;
 };
 
@@ -171,8 +171,7 @@ struct r3964_info {
 
 	struct rx_block_header *rx_first;
 	struct rx_block_header *rx_last;
-	struct tx_block_header *tx_first;
-	struct tx_block_header *tx_last;
+	struct list_head tx_blocks;
 	unsigned int tx_position;
         unsigned int rx_position;
 	unsigned char last_rx;
@@ -316,42 +315,25 @@ static void add_tx_queue(struct r3964_in
 	unsigned long flags;
 
 	spin_lock_irqsave(&pInfo->lock, flags);
-
-	pHeader->next = NULL;
-
-	if (pInfo->tx_last == NULL) {
-		pInfo->tx_first = pInfo->tx_last = pHeader;
-	} else {
-		pInfo->tx_last->next = pHeader;
-		pInfo->tx_last = pHeader;
-	}
-
+	list_add_tail(&pHeader->node, &pInfo->tx_blocks);
 	spin_unlock_irqrestore(&pInfo->lock, flags);
-
-	TRACE_Q("add_tx_queue %p, length %d, tx_first = %p",
-		pHeader, pHeader->length, pInfo->tx_first);
 }
 
 static void remove_from_tx_queue(struct r3964_info *pInfo, int error_code)
 {
 	struct tx_block_header *pHeader;
 	unsigned long flags;
-#ifdef DEBUG_QUEUE
-	struct tx_block_header *pDump;
-#endif
 
-	pHeader = pInfo->tx_first;
-
-	if (pHeader == NULL)
+	spin_lock_irqsave(&pInfo->lock, flags);
+	if (list_empty(&pInfo->tx_blocks)) {
+		spin_unlock_irqrestore(&pInfo->lock, flags);
 		return;
+	}
 
-#ifdef DEBUG_QUEUE
-	printk("r3964: remove_from_tx_queue: %p, length %u - ",
-		pHeader, pHeader->length);
-	for (pDump = pHeader; pDump; pDump = pDump->next)
-		printk("%p ", pDump);
-	printk("\n");
-#endif
+	pHeader = list_first_entry(&pInfo->tx_blocks, struct tx_block_header,
+				   node);
+	list_del(&pHeader->node);
+	spin_unlock_irqrestore(&pInfo->lock, flags);
 
 	if (pHeader->owner) {
 		if (error_code) {
@@ -364,20 +346,7 @@ static void remove_from_tx_queue(struct
 		wake_up_interruptible(&pInfo->tty->read_wait);
 	}
 
-	spin_lock_irqsave(&pInfo->lock, flags);
-
-	pInfo->tx_first = pHeader->next;
-	if (pInfo->tx_first == NULL) {
-		pInfo->tx_last = NULL;
-	}
-
-	spin_unlock_irqrestore(&pInfo->lock, flags);
-
 	kfree(pHeader);
-	TRACE_M("remove_from_tx_queue - kfree %p", pHeader);
-
-	TRACE_Q("remove_from_tx_queue: tx_first = %p, tx_last = %p",
-		pInfo->tx_first, pInfo->tx_last);
 }
 
 static void add_rx_queue(struct r3964_info *pInfo,
@@ -476,7 +445,7 @@ static void trigger_transmit(struct r396
 
 	spin_lock_irqsave(&pInfo->lock, flags);
 
-	if ((pInfo->state == R3964_IDLE) && (pInfo->tx_first != NULL)) {
+	if ((pInfo->state == R3964_IDLE) && (!list_empty(&pInfo->tx_blocks))) {
 		pInfo->state = R3964_TX_REQUEST;
 		pInfo->nRetry = 0;
 		pInfo->flags &= ~R3964_ERROR;
@@ -522,17 +491,19 @@ static void retry_transmit(struct r3964_
 static void transmit_block(struct r3964_info *pInfo)
 {
 	struct tty_struct *tty = pInfo->tty;
-	struct tx_block_header *pBlock = pInfo->tx_first;
-	int room = 0;
+	struct tx_block_header *pBlock;
+	int room;
 
-	if (tty == NULL || pBlock == NULL) {
+	if (!tty)
 		return;
-	}
 
-	room = tty_write_room(tty);
+	if (list_empty(&pInfo->tx_blocks))
+		return;
 
-	TRACE_PS("transmit_block %p, room %d, length %d",
-		 pBlock, room, pBlock->length);
+	pBlock = list_first_entry(&pInfo->tx_blocks, struct tx_block_header,
+				  node);
+
+	room = tty_write_room(tty);
 
 	while (pInfo->tx_position < pBlock->length) {
 		if (room < 2)
@@ -1077,7 +1048,7 @@ static int r3964_open(struct tty_struct
 	pInfo->tty = tty;
 	pInfo->priority = R3964_MASTER;
 	pInfo->rx_first = pInfo->rx_last = NULL;
-	pInfo->tx_first = pInfo->tx_last = NULL;
+	INIT_LIST_HEAD(&pInfo->tx_blocks);
 	pInfo->rx_position = 0;
 	pInfo->tx_position = 0;
 	pInfo->last_rx = 0;
@@ -1100,7 +1071,7 @@ static void r3964_close(struct tty_struc
 	struct r3964_info *pInfo = tty->disc_data;
 	struct r3964_client_info *pClient, *pNext;
 	struct r3964_message *pMsg;
-	struct tx_block_header *pHeader, *pNextHeader;
+	struct tx_block_header *pHeader, *tmp;
 	unsigned long flags;
 
 	TRACE_L("close");
@@ -1129,15 +1100,11 @@ static void r3964_close(struct tty_struc
 	}
 	/* Remove jobs from tx_queue: */
 	spin_lock_irqsave(&pInfo->lock, flags);
-	pHeader = pInfo->tx_first;
-	pInfo->tx_first = pInfo->tx_last = NULL;
-	spin_unlock_irqrestore(&pInfo->lock, flags);
-
-	while (pHeader) {
-		pNextHeader = pHeader->next;
+	list_for_each_entry_safe(pHeader, tmp, &pInfo->tx_blocks, node) {
+		list_del(&pHeader->node);
 		kfree(pHeader);
-		pHeader = pNextHeader;
 	}
+	spin_unlock_irqrestore(&pInfo->lock, flags);
 
 	/* Free buffers: */
 	kfree(pInfo->rx_buf);