0010-tty-n_r3964-for-clients-use-a-real-kernel-list.patch

From 336b06e9db65482b6146e112670cff7e4e52c7ef Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Fri, 25 Jan 2019 09:35:45 +0100
Subject: [PATCH 10/15] tty: n_r3964: for clients, use a real kernel list

The "info" structure had a hand-rolled linked list of all of the clients
associated with it.  Convert that over to a kernel list structure,
making the logic a lot simpler and easier to understand.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_r3964.c |   31 ++++++++++++-------------------
 1 file changed, 12 insertions(+), 19 deletions(-)

--- a/drivers/tty/n_r3964.c
+++ b/drivers/tty/n_r3964.c
@@ -109,8 +109,7 @@ struct r3964_client_info {
 	struct pid *pid;
 	unsigned int sig_flags;
 
-	struct r3964_client_info *next;
-
+	struct list_head node;
 	struct list_head msgs;
 	struct rx_block_header *next_block_to_read;
 	int msg_count;
@@ -178,7 +177,7 @@ struct r3964_info {
 
 	struct mutex read_lock;		/* serialize read and ioctl */
 
-	struct r3964_client_info *firstClient;
+	struct list_head clients;
 	unsigned int state;
 	unsigned int flags;
 
@@ -549,7 +548,7 @@ static void on_receive_block(struct r396
 
 	/* notify attached client processes: */
 	spin_lock_irqsave(&pInfo->lock, flags);
-	for (pClient = pInfo->firstClient; pClient; pClient = pClient->next) {
+	list_for_each_entry(pClient, &pInfo->clients, node) {
 		if (pClient->sig_flags & R3964_SIG_DATA) {
 			add_msg(pClient, R3964_MSG_DATA, length, R3964_OK,
 				pBlock);
@@ -755,11 +754,12 @@ static struct r3964_client_info *findCli
 	unsigned long flags;
 
 	spin_lock_irqsave(&pInfo->lock, flags);
-	for (pClient = pInfo->firstClient; pClient; pClient = pClient->next) {
+	list_for_each_entry(pClient, &pInfo->clients, node) {
 		if (pClient->pid == pid) {
 			goto exit;
 		}
 	}
+	pClient = NULL;
 exit:
 	spin_unlock_irqrestore(&pInfo->lock, flags);
 	return pClient;
@@ -768,7 +768,6 @@ exit:
 static int enable_signals(struct r3964_info *pInfo, struct pid *pid, int arg)
 {
 	struct r3964_client_info *pClient;
-	struct r3964_client_info **ppClient;
 	struct r3964_message *pMsg;
 	unsigned long flags;
 
@@ -776,14 +775,10 @@ static int enable_signals(struct r3964_i
 		spin_lock_irqsave(&pInfo->lock, flags);
 
 		/* Remove client from client list */
-		for (ppClient = &pInfo->firstClient; *ppClient;
-		     ppClient = &(*ppClient)->next) {
-			pClient = *ppClient;
-
+		list_for_each_entry(pClient, &pInfo->clients, node) {
 			if (pClient->pid == pid) {
 				TRACE_PS("removing client %d from client list",
 					 pid_nr(pid));
-				*ppClient = pClient->next;
 				while (pClient->msg_count) {
 					pMsg = remove_msg(pClient);
 					if (pMsg) {
@@ -793,6 +788,7 @@ static int enable_signals(struct r3964_i
 					}
 				}
 				put_pid(pClient->pid);
+				list_del(&pClient->node);
 				kfree(pClient);
 				TRACE_M("enable_signals - kfree %p", pClient);
 				spin_unlock_irqrestore(&pInfo->lock, flags);
@@ -819,11 +815,10 @@ static int enable_signals(struct r3964_i
 			spin_lock_init(&pClient->lock);
 			pClient->sig_flags = arg;
 			pClient->pid = get_pid(pid);
-			pClient->next = pInfo->firstClient;
 			INIT_LIST_HEAD(&pClient->msgs);
 			pClient->next_block_to_read = NULL;
 			pClient->msg_count = 0;
-			pInfo->firstClient = pClient;
+			list_add(&pClient->node, &pInfo->clients);
 			spin_unlock_irqrestore(&pInfo->lock, flags);
 		}
 	}
@@ -1001,7 +996,7 @@ static int r3964_open(struct tty_struct
 	pInfo->tx_position = 0;
 	pInfo->last_rx = 0;
 	pInfo->blocks_in_rx_queue = 0;
-	pInfo->firstClient = NULL;
+	INIT_LIST_HEAD(&pInfo->clients);
 	pInfo->state = R3964_IDLE;
 	pInfo->flags = R3964_DEBUG;
 	pInfo->nRetry = 0;
@@ -1017,7 +1012,7 @@ static int r3964_open(struct tty_struct
 static void r3964_close(struct tty_struct *tty)
 {
 	struct r3964_info *pInfo = tty->disc_data;
-	struct r3964_client_info *pClient, *pNext;
+	struct r3964_client_info *pClient, *tmp_client;
 	struct r3964_message *pMsg;
 	struct tx_block_header *pHeader, *tmp;
 	unsigned long flags;
@@ -1031,9 +1026,7 @@ static void r3964_close(struct tty_struc
 	del_timer_sync(&pInfo->tmr);
 
 	/* Remove client-structs and message queues: */
-	pClient = pInfo->firstClient;
-	while (pClient) {
-		pNext = pClient->next;
+	list_for_each_entry_safe(pClient, tmp_client, &pInfo->clients, node) {
 		while (pClient->msg_count) {
 			pMsg = remove_msg(pClient);
 			if (pMsg) {
@@ -1042,9 +1035,9 @@ static void r3964_close(struct tty_struc
 			}
 		}
 		put_pid(pClient->pid);
+		list_del(&pClient->node);
 		kfree(pClient);
 		TRACE_M("r3964_close - client kfree %p", pClient);
-		pClient = pNext;
 	}
 	/* Remove jobs from tx_queue: */
 	spin_lock_irqsave(&pInfo->lock, flags);