printk, netconsole: implement reliable netconsole

index 9b30871..58b1fec 100644
@@ -30,6 +30,8 @@ static inline const char *printk_skip_level(const char *buffer)
 	return buffer;
 }
 
+#define CONSOLE_EXT_LOG_MAX	8192
+
 /* printk's without a loglevel use this.. */
 #define MESSAGE_LOGLEVEL_DEFAULT CONFIG_MESSAGE_LOGLEVEL_DEFAULT
 

index 879edfc..b6e24af 100644
@@ -512,7 +512,7 @@ struct devkmsg_user {
 	u32 idx;
 	enum log_flags prev;
 	struct mutex lock;
-	char buf[8192];
+	char buf[CONSOLE_EXT_LOG_MAX];
 };
 
 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)

@@ -565,11 +565,18 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
 	return ret;
 }
 
+static void append_char(char **pp, char *e, char c)
+{
+	if (*pp < e)
+		*(*pp)++ = c;
+}
+
 static ssize_t devkmsg_read(struct file *file, char __user *buf,
 			    size_t count, loff_t *ppos)
 {
 	struct devkmsg_user *user = file->private_data;
 	struct printk_log *msg;
+	char *p, *e;
 	u64 ts_usec;
 	size_t i;
 	char cont = '-';

@@ -579,6 +586,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	if (!user)
 		return -EBADF;
 
+	p = user->buf;
+	e = user->buf + sizeof(user->buf);
+
 	ret = mutex_lock_interruptible(&user->lock);
 	if (ret)
 		return ret;

@@ -625,9 +635,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 		 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
 		cont = '+';
 
-	len = sprintf(user->buf, "%u,%llu,%llu,%c;",
-		      (msg->facility << 3) | msg->level,
-		      user->seq, ts_usec, cont);
+	p += scnprintf(p, e - p, "%u,%llu,%llu,%c;",
+		       (msg->facility << 3) | msg->level,
+		       user->seq, ts_usec, cont);
 	user->prev = msg->flags;
 
 	/* escape non-printable characters */

@@ -635,11 +645,11 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 		unsigned char c = log_text(msg)[i];
 
 		if (c < ' ' || c >= 127 || c == '\\')
-			len += sprintf(user->buf + len, "\\x%02x", c);
+			p += scnprintf(p, e - p, "\\x%02x", c);
 		else
-			user->buf[len++] = c;
+			append_char(&p, e, c);
 	}
-	user->buf[len++] = '\n';
+	append_char(&p, e, '\n');
 
 	if (msg->dict_len) {
 		bool line = true;

@@ -648,30 +658,31 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 			unsigned char c = log_dict(msg)[i];
 
 			if (line) {
-				user->buf[len++] = ' ';
+				append_char(&p, e, ' ');
 				line = false;
 			}
 
 			if (c == '\0') {
-				user->buf[len++] = '\n';
+				append_char(&p, e, '\n');
 				line = true;
 				continue;
 			}
 
 			if (c < ' ' || c >= 127 || c == '\\') {
-				len += sprintf(user->buf + len, "\\x%02x", c);
+				p += scnprintf(p, e - p, "\\x%02x", c);
 				continue;
 			}
 
-			user->buf[len++] = c;
+			append_char(&p, e, c);
 		}
-		user->buf[len++] = '\n';
+		append_char(&p, e, '\n');
 	}
 
 	user->idx = log_next(user->idx);
 	user->seq++;
 	raw_spin_unlock_irq(&logbuf_lock);
 
+	len = p - user->buf;
 	if (len > count) {
 		ret = -EINVAL;
 		goto out;

index b6e24af..5ea6709 100644
@@ -505,6 +505,86 @@ int check_syslog_permissions(int type, bool from_file)
 	return security_syslog(type);
 }
 
+static void append_char(char **pp, char *e, char c)
+{
+	if (*pp < e)
+		*(*pp)++ = c;
+}
+
+static ssize_t msg_print_ext_header(char *buf, size_t size,
+				    struct printk_log *msg, u64 seq,
+				    enum log_flags prev_flags)
+{
+	u64 ts_usec = msg->ts_nsec;
+	char cont = '-';
+
+	do_div(ts_usec, 1000);
+
+	/*
+	 * If we couldn't merge continuation line fragments during the print,
+	 * export the stored flags to allow an optional external merge of the
+	 * records. Merging the records isn't always neccessarily correct, like
+	 * when we hit a race during printing. In most cases though, it produces
+	 * better readable output. 'c' in the record flags mark the first
+	 * fragment of a line, '+' the following.
+	 */
+	if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
+		cont = 'c';
+	else if ((msg->flags & LOG_CONT) ||
+		 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
+		cont = '+';
+
+	return scnprintf(buf, size, "%u,%llu,%llu,%c;",
+		       (msg->facility << 3) | msg->level, seq, ts_usec, cont);
+}
+
+static ssize_t msg_print_ext_body(char *buf, size_t size,
+				  char *dict, size_t dict_len,
+				  char *text, size_t text_len)
+{
+	char *p = buf, *e = buf + size;
+	size_t i;
+
+	/* escape non-printable characters */
+	for (i = 0; i < text_len; i++) {
+		unsigned char c = text[i];
+
+		if (c < ' ' || c >= 127 || c == '\\')
+			p += scnprintf(p, e - p, "\\x%02x", c);
+		else
+			append_char(&p, e, c);
+	}
+	append_char(&p, e, '\n');
+
+	if (dict_len) {
+		bool line = true;
+
+		for (i = 0; i < dict_len; i++) {
+			unsigned char c = dict[i];
+
+			if (line) {
+				append_char(&p, e, ' ');
+				line = false;
+			}
+
+			if (c == '\0') {
+				append_char(&p, e, '\n');
+				line = true;
+				continue;
+			}
+
+			if (c < ' ' || c >= 127 || c == '\\') {
+				p += scnprintf(p, e - p, "\\x%02x", c);
+				continue;
+			}
+
+			append_char(&p, e, c);
+		}
+		append_char(&p, e, '\n');
+	}
+
+	return p - buf;
+}
 
 /* /dev/kmsg - userspace message inject/listen interface */
 struct devkmsg_user {

@@ -565,30 +645,17 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
 	return ret;
 }
 
-static void append_char(char **pp, char *e, char c)
-{
-	if (*pp < e)
-		*(*pp)++ = c;
-}
-
 static ssize_t devkmsg_read(struct file *file, char __user *buf,
 			    size_t count, loff_t *ppos)
 {
 	struct devkmsg_user *user = file->private_data;
 	struct printk_log *msg;
-	char *p, *e;
-	u64 ts_usec;
-	size_t i;
-	char cont = '-';
 	size_t len;
 	ssize_t ret;
 
 	if (!user)
 		return -EBADF;
 
-	p = user->buf;
-	e = user->buf + sizeof(user->buf);
-
 	ret = mutex_lock_interruptible(&user->lock);
 	if (ret)
 		return ret;

@@ -618,71 +685,17 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	}
 
 	msg = log_from_idx(user->idx);
-	ts_usec = msg->ts_nsec;
-	do_div(ts_usec, 1000);
-
-	/*
-	 * If we couldn't merge continuation line fragments during the print,
-	 * export the stored flags to allow an optional external merge of the
-	 * records. Merging the records isn't always neccessarily correct, like
-	 * when we hit a race during printing. In most cases though, it produces
-	 * better readable output. 'c' in the record flags mark the first
-	 * fragment of a line, '+' the following.
-	 */
-	if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
-		cont = 'c';
-	else if ((msg->flags & LOG_CONT) ||
-		 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
-		cont = '+';
+	len = msg_print_ext_header(user->buf, sizeof(user->buf),
+				   msg, user->seq, user->prev);
+	len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
+				  log_dict(msg), msg->dict_len,
+				  log_text(msg), msg->text_len);
 
-	p += scnprintf(p, e - p, "%u,%llu,%llu,%c;",
-		       (msg->facility << 3) | msg->level,
-		       user->seq, ts_usec, cont);
 	user->prev = msg->flags;
-
-	/* escape non-printable characters */
-	for (i = 0; i < msg->text_len; i++) {
-		unsigned char c = log_text(msg)[i];
-
-		if (c < ' ' || c >= 127 || c == '\\')
-			p += scnprintf(p, e - p, "\\x%02x", c);
-		else
-			append_char(&p, e, c);
-	}
-	append_char(&p, e, '\n');
-
-	if (msg->dict_len) {
-		bool line = true;
-
-		for (i = 0; i < msg->dict_len; i++) {
-			unsigned char c = log_dict(msg)[i];
-
-			if (line) {
-				append_char(&p, e, ' ');
-				line = false;
-			}
-
-			if (c == '\0') {
-				append_char(&p, e, '\n');
-				line = true;
-				continue;
-			}
-
-			if (c < ' ' || c >= 127 || c == '\\') {
-				p += scnprintf(p, e - p, "\\x%02x", c);
-				continue;
-			}
-
-			append_char(&p, e, c);
-		}
-		append_char(&p, e, '\n');
-	}
-
 	user->idx = log_next(user->idx);
 	user->seq++;
 	raw_spin_unlock_irq(&logbuf_lock);
 
-	len = p - user->buf;
 	if (len > count) {
 		ret = -EINVAL;
 		goto out;

index 5ea6709..0175c46 100644
@@ -1417,7 +1417,8 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
  * log_buf[start] to log_buf[end - 1].
  * The console_lock must be held.
  */
-static void call_console_drivers(int level, const char *text, size_t len)
+static void call_console_drivers(int level, bool nocons,
+				 const char *text, size_t len)
 {
 	struct console *con;
 

@@ -1438,6 +1439,13 @@ static void call_console_drivers(int level, const char *text, size_t len)
 		if (!cpu_online(smp_processor_id()) &&
 		    !(con->flags & CON_ANYTIME))
 			continue;
+		/*
+		 * Skip record we have buffered and already printed
+		 * directly to the console when we received it.
+		 */
+		if (nocons)
+			continue;
+
 		con->write(con, text, len);
 	}
 }

@@ -1919,7 +1927,8 @@ static struct cont {
 } cont;
 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
 static u32 log_next(u32 idx) { return 0; }
-static void call_console_drivers(int level, const char *text, size_t len) {}
+static void call_console_drivers(int level, bool nocons,
+				 const char *text, size_t len) {}
 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
 			     bool syslog, char *buf, size_t size) { return 0; }
 static size_t cont_print_text(char *text, size_t size) { return 0; }

@@ -2190,7 +2199,7 @@ static void console_cont_flush(char *text, size_t size)
 	len = cont_print_text(text, size);
 	raw_spin_unlock(&logbuf_lock);
 	stop_critical_timings();
-	call_console_drivers(cont.level, text, len);
+	call_console_drivers(cont.level, false, text, len);
 	start_critical_timings();
 	local_irq_restore(flags);
 	return;

@@ -2234,6 +2243,7 @@ again:
 		struct printk_log *msg;
 		size_t len;
 		int level;
+		bool nocons;
 
 		raw_spin_lock_irqsave(&logbuf_lock, flags);
 		if (seen_seq != log_next_seq) {

@@ -2252,38 +2262,30 @@ again:
 		} else {
 			len = 0;
 		}
-skip:
+
 		if (console_seq == log_next_seq)
 			break;
 
 		msg = log_from_idx(console_idx);
-		if (msg->flags & LOG_NOCONS) {
-			/*
-			 * Skip record we have buffered and already printed
-			 * directly to the console when we received it.
-			 */
-			console_idx = log_next(console_idx);
-			console_seq++;
-			/*
-			 * We will get here again when we register a new
-			 * CON_PRINTBUFFER console. Clear the flag so we
-			 * will properly dump everything later.
-			 */
-			msg->flags &= ~LOG_NOCONS;
-			console_prev = msg->flags;
-			goto skip;
-		}
-
 		level = msg->level;
+		nocons = msg->flags & LOG_NOCONS;
 		len += msg_print_text(msg, console_prev, false,
 				      text + len, sizeof(text) - len);
 		console_idx = log_next(console_idx);
 		console_seq++;
 		console_prev = msg->flags;
+
+		/*
+		 * The log will be processed again when we register a new
+		 * CON_PRINTBUFFER console. Clear the flag so we will
+		 * properly dump everything later.
+		 */
+		msg->flags &= ~LOG_NOCONS;
+
 		raw_spin_unlock(&logbuf_lock);
 
 		stop_critical_timings();	/* don't trace print latency */
-		call_console_drivers(level, text, len);
+		call_console_drivers(level, nocons, text, len);
 		start_critical_timings();
 		local_irq_restore(flags);
 	}

index 7571a16..04bbd09 100644
@@ -115,6 +115,7 @@ static inline int con_debug_leave(void)
 #define CON_BOOT	(8)
 #define CON_ANYTIME	(16) /* Safe to call when cpu is offline */
 #define CON_BRL		(32) /* Used for a braille device */
+#define CON_EXTENDED	(64) /* Use the extended output format a la /dev/kmsg */
 
 struct console {
 	char	name[16];

296 lines not on this page · raw message

index 58b1fec..4fd3bb4 100644
@@ -6,6 +6,7 @@
 #include <linux/kern_levels.h>
 #include <linux/linkage.h>
 #include <linux/cache.h>
+#include <linux/errno.h>
 
 extern const char linux_banner[];
 extern const char linux_proc_banner[];

@@ -169,6 +170,8 @@ void __init setup_log_buf(int early);
 void dump_stack_set_arch_desc(const char *fmt, ...);
 void dump_stack_print_info(const char *log_lvl);
 void show_regs_print_info(const char *log_lvl);
+void log_seq_range(u64 *beginp, u64 *endp);
+ssize_t ext_log_from_seq(char *buf, size_t size, u64 log_seq);
 #else
 static inline __printf(1, 0)
 int vprintk(const char *s, va_list args)

@@ -228,6 +231,17 @@ static inline void dump_stack_print_info(const char *log_lvl)
 static inline void show_regs_print_info(const char *log_lvl)
 {
 }
+
+static inline void log_seq_range(u64 *begin_seqp, u64 *end_seqp)
+{
+	*begin_seqp = 0;
+	*end_seqp = 0;
+}
+
+static inline ssize_t ext_log_from_seq(char *buf, size_t size, u64 log_seq)
+{
+	return -ERANGE;
+}
 #endif
 
 extern asmlinkage void dump_stack(void) __cold;

102 lines not on this page · raw message

index 15731d1..09d4e12 100644
@@ -104,7 +104,7 @@ struct netconsole_target {
 #ifdef	CONFIG_NETCONSOLE_DYNAMIC
 	struct config_item	item;
 #endif
-	int			enabled;
+	bool			enabled;
 	struct mutex		mutex;
 	struct netpoll		np;
 };

@@ -197,7 +197,7 @@ static struct netconsole_target *alloc_param_target(char *target_config)
 	if (err)
 		goto fail;
 
-	nt->enabled = 1;
+	nt->enabled = true;
 
 	return nt;
 

@@ -322,13 +322,13 @@ static ssize_t store_enabled(struct netconsole_target *nt,
 		return err;
 	if (enabled < 0 || enabled > 1)
 		return -EINVAL;
-	if (enabled == nt->enabled) {
+	if ((bool)enabled == nt->enabled) {
 		pr_info("network logging has already %s\n",
 			nt->enabled ? "started" : "stopped");
 		return -EINVAL;
 	}
 
-	if (enabled) {	/* 1 */
+	if (enabled) {	/* true */
 		/*
 		 * Skip netpoll_parse_options() -- all the attributes are
 		 * already configured via configfs. Just print them out.

@@ -340,13 +340,13 @@ static ssize_t store_enabled(struct netconsole_target *nt,
 			return err;
 
 		pr_info("netconsole: network logging started\n");
-	} else {	/* 0 */
+	} else {	/* false */
 		/* We need to disable the netconsole before cleaning it up
 		 * otherwise we might end up in write_msg() with
-		 * nt->np.dev == NULL and nt->enabled == 1
+		 * nt->np.dev == NULL and nt->enabled == true
 		 */
 		spin_lock_irqsave(&target_list_lock, flags);
-		nt->enabled = 0;
+		nt->enabled = false;
 		spin_unlock_irqrestore(&target_list_lock, flags);
 		netpoll_cleanup(&nt->np);
 	}

@@ -594,7 +594,7 @@ static struct config_item *make_netconsole_target(struct config_group *group,
 
 	/*
 	 * Allocate and initialize with defaults.
-	 * Target is disabled at creation (enabled == 0).
+	 * Target is disabled at creation (!enabled).
 	 */
 	nt = kzalloc(sizeof(*nt), GFP_KERNEL);
 	if (!nt)

@@ -695,7 +695,7 @@ restart:
 				spin_lock_irqsave(&target_list_lock, flags);
 				dev_put(nt->np.dev);
 				nt->np.dev = NULL;
-				nt->enabled = 0;
+				nt->enabled = false;
 				stopped = true;
 				netconsole_target_put(nt);
 				goto restart;

index 09d4e12..17692b8 100644
@@ -167,19 +167,17 @@ static void netconsole_target_put(struct netconsole_target *nt)
 
 #endif	/* CONFIG_NETCONSOLE_DYNAMIC */
 
-/* Allocate new target (from boot/module param) and setup netpoll for it */
-static struct netconsole_target *alloc_param_target(char *target_config)
+/*
+ * Allocate and initialize with defaults.  Note that these targets get
+ * their config_item fields zeroed-out.
+ */
+static struct netconsole_target *alloc_netconsole_target(void)
 {
-	int err = -ENOMEM;
 	struct netconsole_target *nt;
 
-	/*
-	 * Allocate and initialize with defaults.
-	 * Note that these targets get their config_item fields zeroed-out.
-	 */
 	nt = kzalloc(sizeof(*nt), GFP_KERNEL);
 	if (!nt)
-		goto fail;
+		return NULL;
 
 	nt->np.name = "netconsole";
 	strlcpy(nt->np.dev_name, "eth0", IFNAMSIZ);

@@ -188,6 +186,19 @@ static struct netconsole_target *alloc_param_target(char *target_config)
 	mutex_init(&nt->mutex);
 	eth_broadcast_addr(nt->np.remote_mac);
 
+	return nt;
+}
+
+/* Allocate new target (from boot/module param) and setup netpoll for it */
+static struct netconsole_target *alloc_param_target(char *target_config)
+{
+	int err = -ENOMEM;
+	struct netconsole_target *nt;
+
+	nt = alloc_netconsole_target();
+	if (!nt)
+		goto fail;
+
 	/* Parse parameters and setup netpoll */
 	err = netpoll_parse_options(&nt->np, target_config);
 	if (err)

@@ -592,21 +603,10 @@ static struct config_item *make_netconsole_target(struct config_group *group,
 	unsigned long flags;
 	struct netconsole_target *nt;
 
-	/*
-	 * Allocate and initialize with defaults.
-	 * Target is disabled at creation (!enabled).
-	 */
-	nt = kzalloc(sizeof(*nt), GFP_KERNEL);
+	nt = alloc_netconsole_target();
 	if (!nt)
 		return ERR_PTR(-ENOMEM);
 
-	nt->np.name = "netconsole";
-	strlcpy(nt->np.dev_name, "eth0", IFNAMSIZ);
-	nt->np.local_port = 6665;
-	nt->np.remote_port = 6666;
-	mutex_init(&nt->mutex);
-	eth_broadcast_addr(nt->np.remote_mac);
-
 	/* Initialize the config_item member */
 	config_item_init_type_name(&nt->item, name, &netconsole_target_type);
 

index 17692b8..d355776 100644
@@ -105,6 +105,7 @@ struct netconsole_target {
 	struct config_item	item;
 #endif
 	bool			enabled;
+	bool			disable_scheduled;
 	struct mutex		mutex;
 	struct netpoll		np;
 };

@@ -660,6 +661,39 @@ static struct configfs_subsystem netconsole_subsys = {
 
 #endif	/* CONFIG_NETCONSOLE_DYNAMIC */
 
+static void netconsole_deferred_disable_work_fn(struct work_struct *work)
+{
+	struct netconsole_target *nt, *to_disable;
+	unsigned long flags;
+
+repeat:
+	to_disable = NULL;
+	spin_lock_irqsave(&target_list_lock, flags);
+	list_for_each_entry(nt, &target_list, list) {
+		if (!nt->disable_scheduled)
+			continue;
+		nt->disable_scheduled = false;
+
+		if (!nt->enabled)
+			continue;
+
+		netconsole_target_get(nt);
+		nt->enabled = false;
+		to_disable = nt;
+		break;
+	}
+	spin_unlock_irqrestore(&target_list_lock, flags);
+
+	if (to_disable) {
+		netpoll_cleanup(&to_disable->np);
+		netconsole_target_put(to_disable);
+		goto repeat;
+	}
+}
+
+static DECLARE_WORK(netconsole_deferred_disable_work,
+		    netconsole_deferred_disable_work_fn);
+
 /* Handle network interface device notifications */
 static int netconsole_netdev_event(struct notifier_block *this,
 				   unsigned long event, void *ptr)

@@ -674,9 +708,7 @@ static int netconsole_netdev_event(struct notifier_block *this,
 		goto done;
 
 	spin_lock_irqsave(&target_list_lock, flags);
-restart:
 	list_for_each_entry(nt, &target_list, list) {
-		netconsole_target_get(nt);
 		if (nt->np.dev == dev) {
 			switch (event) {
 			case NETDEV_CHANGENAME:

@@ -685,23 +717,14 @@ restart:
 			case NETDEV_RELEASE:
 			case NETDEV_JOIN:
 			case NETDEV_UNREGISTER:
-				/* rtnl_lock already held
-				 * we might sleep in __netpoll_cleanup()
-				 */
-				spin_unlock_irqrestore(&target_list_lock, flags);
-
-				__netpoll_cleanup(&nt->np);
-
-				spin_lock_irqsave(&target_list_lock, flags);
-				dev_put(nt->np.dev);
-				nt->np.dev = NULL;
-				nt->enabled = false;
+				/* rtnl_lock already held, punt to workqueue */
+				if (nt->enabled && !nt->disable_scheduled) {
+					nt->disable_scheduled = true;
+					schedule_work(&netconsole_deferred_disable_work);
+				}
 				stopped = true;
-				netconsole_target_put(nt);
-				goto restart;
 			}
 		}
-		netconsole_target_put(nt);
 	}
 	spin_unlock_irqrestore(&target_list_lock, flags);
 	if (stopped) {

@@ -810,7 +833,7 @@ static int __init init_netconsole(void)
 
 undonotifier:
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);
-
+	cancel_work_sync(&netconsole_deferred_disable_work);
 fail:
 	pr_err("cleaning up\n");
 

@@ -834,6 +857,7 @@ static void __exit cleanup_netconsole(void)
 	unregister_console(&netconsole);
 	dynamic_netconsole_exit();
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);
+	cancel_work_sync(&netconsole_deferred_disable_work);
 
 	/*
 	 * Targets created via configfs pin references on our module

index d355776..57c02ab 100644
@@ -73,12 +73,12 @@ static int __init option_setup(char *opt)
 __setup("netconsole=", option_setup);
 #endif	/* MODULE */
 
-/* Linked list of all configured targets */
+/*
+ * Linked list of all configured targets.  The list and each target's
+ * enable/disable state are protected by console_lock.
+ */
 static LIST_HEAD(target_list);
 
-/* This needs to be a spinlock because write_msg() cannot sleep */
-static DEFINE_SPINLOCK(target_list_lock);
-
 /**
  * struct netconsole_target - Represents a configured netconsole target.
  * @list:	Links this target into the target_list.

@@ -325,7 +325,6 @@ static ssize_t store_enabled(struct netconsole_target *nt,
 			     const char *buf,
 			     size_t count)
 {
-	unsigned long flags;
 	int enabled;
 	int err;
 

@@ -357,9 +356,9 @@ static ssize_t store_enabled(struct netconsole_target *nt,
 		 * otherwise we might end up in write_msg() with
 		 * nt->np.dev == NULL and nt->enabled == true
 		 */
-		spin_lock_irqsave(&target_list_lock, flags);
+		console_lock();
 		nt->enabled = false;
-		spin_unlock_irqrestore(&target_list_lock, flags);
+		console_unlock();
 		netpoll_cleanup(&nt->np);
 	}
 

@@ -601,7 +600,6 @@ static struct config_item_type netconsole_target_type = {
 static struct config_item *make_netconsole_target(struct config_group *group,
 						  const char *name)
 {
-	unsigned long flags;
 	struct netconsole_target *nt;
 
 	nt = alloc_netconsole_target();

@@ -612,9 +610,9 @@ static struct config_item *make_netconsole_target(struct config_group *group,
 	config_item_init_type_name(&nt->item, name, &netconsole_target_type);
 
 	/* Adding, but it is disabled */
-	spin_lock_irqsave(&target_list_lock, flags);
+	console_lock();
 	list_add(&nt->list, &target_list);
-	spin_unlock_irqrestore(&target_list_lock, flags);
+	console_unlock();
 
 	return &nt->item;
 }

@@ -622,12 +620,11 @@ static struct config_item *make_netconsole_target(struct config_group *group,
 static void drop_netconsole_target(struct config_group *group,
 				   struct config_item *item)
 {
-	unsigned long flags;
 	struct netconsole_target *nt = to_target(item);
 
-	spin_lock_irqsave(&target_list_lock, flags);
+	console_lock();
 	list_del(&nt->list);
-	spin_unlock_irqrestore(&target_list_lock, flags);
+	console_unlock();
 
 	/*
 	 * The target may have never been enabled, or was manually disabled

@@ -664,11 +661,10 @@ static struct configfs_subsystem netconsole_subsys = {
 static void netconsole_deferred_disable_work_fn(struct work_struct *work)
 {
 	struct netconsole_target *nt, *to_disable;
-	unsigned long flags;
 
 repeat:
 	to_disable = NULL;
-	spin_lock_irqsave(&target_list_lock, flags);
+	console_lock();
 	list_for_each_entry(nt, &target_list, list) {
 		if (!nt->disable_scheduled)
 			continue;

@@ -682,7 +678,7 @@ repeat:
 		to_disable = nt;
 		break;
 	}
-	spin_unlock_irqrestore(&target_list_lock, flags);
+	console_unlock();
 
 	if (to_disable) {
 		netpoll_cleanup(&to_disable->np);

@@ -698,7 +694,6 @@ static DECLARE_WORK(netconsole_deferred_disable_work,
 static int netconsole_netdev_event(struct notifier_block *this,
 				   unsigned long event, void *ptr)
 {
-	unsigned long flags;
 	struct netconsole_target *nt;
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	bool stopped = false;

@@ -707,7 +702,7 @@ static int netconsole_netdev_event(struct notifier_block *this,
 	      event == NETDEV_RELEASE || event == NETDEV_JOIN))
 		goto done;
 
-	spin_lock_irqsave(&target_list_lock, flags);
+	console_lock();
 	list_for_each_entry(nt, &target_list, list) {
 		if (nt->np.dev == dev) {
 			switch (event) {

@@ -726,7 +721,7 @@ static int netconsole_netdev_event(struct notifier_block *this,
 			}
 		}
 	}
-	spin_unlock_irqrestore(&target_list_lock, flags);
+	console_unlock();
 	if (stopped) {
 		const char *msg = "had an event";
 		switch (event) {

@@ -755,7 +750,6 @@ static struct notifier_block netconsole_netdev_notifier = {
 static void write_msg(struct console *con, const char *msg, unsigned int len)
 {
 	int frag, left;
-	unsigned long flags;
 	struct netconsole_target *nt;
 	const char *tmp;
 

@@ -765,9 +759,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 	if (list_empty(&target_list))
 		return;
 
-	spin_lock_irqsave(&target_list_lock, flags);
 	list_for_each_entry(nt, &target_list, list) {
-		netconsole_target_get(nt);
 		if (nt->enabled && netif_running(nt->np.dev)) {
 			/*
 			 * We nest this inside the for-each-target loop above

@@ -783,9 +775,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 				left -= frag;
 			}
 		}
-		netconsole_target_put(nt);
 	}
-	spin_unlock_irqrestore(&target_list_lock, flags);
 }
 
 static struct console netconsole = {

@@ -798,7 +788,6 @@ static int __init init_netconsole(void)
 {
 	int err;
 	struct netconsole_target *nt, *tmp;
-	unsigned long flags;
 	char *target_config;
 	char *input = config;
 

@@ -812,9 +801,9 @@ static int __init init_netconsole(void)
 			/* Dump existing printks when we register */
 			netconsole.flags |= CON_PRINTBUFFER;
 
-			spin_lock_irqsave(&target_list_lock, flags);
+			console_lock();
 			list_add(&nt->list, &target_list);
-			spin_unlock_irqrestore(&target_list_lock, flags);
+			console_unlock();
 		}
 	}
 

@@ -839,8 +828,8 @@ fail:
 
 	/*
 	 * Remove all targets and destroy them (only targets created
-	 * from the boot/module option exist here). Skipping the list
-	 * lock is safe here, and netpoll_cleanup() will sleep.
+	 * from the boot/module option exist here). Skipping the console
+	 * lock is safe here.
 	 */
 	list_for_each_entry_safe(nt, tmp, &target_list, list) {
 		list_del(&nt->list);

@@ -864,8 +853,7 @@ static void __exit cleanup_netconsole(void)
 	 * and would first be rmdir(2)'ed from userspace. We reach
 	 * here only when they are already destroyed, and only those
 	 * created from the boot/module option are left, so remove and
-	 * destroy them. Skipping the list lock is safe here, and
-	 * netpoll_cleanup() will sleep.
+	 * destroy them. Skipping the console lock is safe here.
 	 */
 	list_for_each_entry_safe(nt, tmp, &target_list, list) {
 		list_del(&nt->list);

index 57c02ab..f0ac9f6 100644
@@ -75,10 +75,14 @@ __setup("netconsole=", option_setup);
 
 /*
  * Linked list of all configured targets.  The list and each target's
- * enable/disable state are protected by console_lock.
+ * enable/disable state are protected by both netconsole_mutex and
+ * console_lock.
  */
 static LIST_HEAD(target_list);
 
+/* protects target creation/destruction and enable/disable */
+static DEFINE_MUTEX(netconsole_mutex);
+
 /**
  * struct netconsole_target - Represents a configured netconsole target.
  * @list:	Links this target into the target_list.

@@ -106,7 +110,6 @@ struct netconsole_target {
 #endif
 	bool			enabled;
 	bool			disable_scheduled;
-	struct mutex		mutex;
 	struct netpoll		np;
 };
 

@@ -184,7 +187,6 @@ static struct netconsole_target *alloc_netconsole_target(void)
 	strlcpy(nt->np.dev_name, "eth0", IFNAMSIZ);
 	nt->np.local_port = 6665;
 	nt->np.remote_port = 6666;
-	mutex_init(&nt->mutex);
 	eth_broadcast_addr(nt->np.remote_mac);
 
 	return nt;

@@ -196,6 +198,8 @@ static struct netconsole_target *alloc_param_target(char *target_config)
 	int err = -ENOMEM;
 	struct netconsole_target *nt;
 
+	lockdep_assert_held(&netconsole_mutex);
+
 	nt = alloc_netconsole_target();
 	if (!nt)
 		goto fail;

@@ -573,10 +577,10 @@ static ssize_t netconsole_target_attr_store(struct config_item *item,
 	struct netconsole_target_attr *na =
 		container_of(attr, struct netconsole_target_attr, attr);
 
-	mutex_lock(&nt->mutex);
+	mutex_lock(&netconsole_mutex);
 	if (na->store)
 		ret = na->store(nt, buf, count);
-	mutex_unlock(&nt->mutex);
+	mutex_unlock(&netconsole_mutex);
 
 	return ret;
 }

@@ -610,9 +614,11 @@ static struct config_item *make_netconsole_target(struct config_group *group,
 	config_item_init_type_name(&nt->item, name, &netconsole_target_type);
 
 	/* Adding, but it is disabled */
+	mutex_lock(&netconsole_mutex);
 	console_lock();
 	list_add(&nt->list, &target_list);
 	console_unlock();
+	mutex_unlock(&netconsole_mutex);
 
 	return &nt->item;
 }

@@ -622,6 +628,7 @@ static void drop_netconsole_target(struct config_group *group,
 {
 	struct netconsole_target *nt = to_target(item);
 
+	mutex_lock(&netconsole_mutex);
 	console_lock();
 	list_del(&nt->list);
 	console_unlock();

@@ -634,6 +641,7 @@ static void drop_netconsole_target(struct config_group *group,
 		netpoll_cleanup(&nt->np);
 
 	config_item_put(&nt->item);
+	mutex_unlock(&netconsole_mutex);
 }
 
 static struct configfs_group_operations netconsole_subsys_group_ops = {

@@ -662,6 +670,7 @@ static void netconsole_deferred_disable_work_fn(struct work_struct *work)
 {
 	struct netconsole_target *nt, *to_disable;
 
+	mutex_lock(&netconsole_mutex);
 repeat:
 	to_disable = NULL;
 	console_lock();

@@ -685,6 +694,8 @@ repeat:
 		netconsole_target_put(to_disable);
 		goto repeat;
 	}
+
+	mutex_unlock(&netconsole_mutex);
 }
 
 static DECLARE_WORK(netconsole_deferred_disable_work,

@@ -791,6 +802,8 @@ static int __init init_netconsole(void)
 	char *target_config;
 	char *input = config;
 
+	mutex_lock(&netconsole_mutex);
+
 	if (strnlen(input, MAX_PARAM_LENGTH)) {
 		while ((target_config = strsep(&input, ";"))) {
 			nt = alloc_param_target(target_config);

@@ -818,24 +831,21 @@ static int __init init_netconsole(void)
 	register_console(&netconsole);
 	pr_info("network logging started\n");
 
+	mutex_unlock(&netconsole_mutex);
 	return err;
 
 undonotifier:
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);
-	cancel_work_sync(&netconsole_deferred_disable_work);
 fail:
 	pr_err("cleaning up\n");
 
-	/*
-	 * Remove all targets and destroy them (only targets created
-	 * from the boot/module option exist here). Skipping the console
-	 * lock is safe here.
-	 */
+	/* targets are already inactive, skipping the console lock is safe */
 	list_for_each_entry_safe(nt, tmp, &target_list, list) {
 		list_del(&nt->list);
 		free_param_target(nt);
 	}
-
+	mutex_unlock(&netconsole_mutex);
+	cancel_work_sync(&netconsole_deferred_disable_work);
 	return err;
 }
 

@@ -843,22 +853,20 @@ static void __exit cleanup_netconsole(void)
 {
 	struct netconsole_target *nt, *tmp;
 
+	mutex_lock(&netconsole_mutex);
+
 	unregister_console(&netconsole);
 	dynamic_netconsole_exit();
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);
-	cancel_work_sync(&netconsole_deferred_disable_work);
 
-	/*
-	 * Targets created via configfs pin references on our module
-	 * and would first be rmdir(2)'ed from userspace. We reach
-	 * here only when they are already destroyed, and only those
-	 * created from the boot/module option are left, so remove and
-	 * destroy them. Skipping the console lock is safe here.
-	 */
+	/* targets are already inactive, skipping the console lock is safe */
 	list_for_each_entry_safe(nt, tmp, &target_list, list) {
 		list_del(&nt->list);
 		free_param_target(nt);
 	}
+
+	mutex_unlock(&netconsole_mutex);
+	cancel_work_sync(&netconsole_deferred_disable_work);
 }
 
 /*

index f0ac9f6..d72d902 100644
@@ -83,6 +83,8 @@ static LIST_HEAD(target_list);
 /* protects target creation/destruction and enable/disable */
 static DEFINE_MUTEX(netconsole_mutex);
 
+static struct console netconsole;
+
 /**
  * struct netconsole_target - Represents a configured netconsole target.
  * @list:	Links this target into the target_list.

@@ -192,8 +194,43 @@ static struct netconsole_target *alloc_netconsole_target(void)
 	return nt;
 }
 
+static int netconsole_enable(struct netconsole_target *nt)
+{
+	int err;
+
+	lockdep_assert_held(&netconsole_mutex);
+	WARN_ON_ONCE(nt->enabled);
+
+	err = netpoll_setup(&nt->np);
+	if (err)
+		return err;
+
+	console_lock();
+	nt->enabled = true;
+	console_unlock();
+	return 0;
+}
+
+static void netconsole_disable(struct netconsole_target *nt)
+{
+	lockdep_assert_held(&netconsole_mutex);
+
+	/*
+	 * We need to disable the netconsole before cleaning it up
+	 * otherwise we might end up in write_msg() with !nt->np.dev &&
+	 * nt->enabled.
+	 */
+	if (nt->enabled) {
+		console_lock();
+		nt->enabled = false;
+		console_unlock();
+
+		netpoll_cleanup(&nt->np);
+	}
+}
+
 /* Allocate new target (from boot/module param) and setup netpoll for it */
-static struct netconsole_target *alloc_param_target(char *target_config)
+static int create_param_target(char *target_config)
 {
 	int err = -ENOMEM;
 	struct netconsole_target *nt;

@@ -209,24 +246,26 @@ static struct netconsole_target *alloc_param_target(char *target_config)
 	if (err)
 		goto fail;
 
-	err = netpoll_setup(&nt->np);
+	console_lock();
+	list_add(&nt->list, &target_list);
+	console_unlock();
+
+	err = netconsole_enable(nt);
 	if (err)
-		goto fail;
+		goto fail_del;
 
-	nt->enabled = true;
+	/* Dump existing printks when we register */
+	netconsole.flags |= CON_PRINTBUFFER;
 
-	return nt;
+	return 0;
 
+fail_del:
+	console_lock();
+	list_del(&nt->list);
+	console_unlock();
 fail:
 	kfree(nt);
-	return ERR_PTR(err);
-}
-
-/* Cleanup netpoll for given target (from boot/module param) and free it */
-static void free_param_target(struct netconsole_target *nt)
-{
-	netpoll_cleanup(&nt->np);
-	kfree(nt);
+	return err;
 }
 
 #ifdef	CONFIG_NETCONSOLE_DYNAMIC

@@ -350,24 +389,15 @@ static ssize_t store_enabled(struct netconsole_target *nt,
 		 */
 		netpoll_print_options(&nt->np);
 
-		err = netpoll_setup(&nt->np);
+		err = netconsole_enable(nt);
 		if (err)
 			return err;
 
 		pr_info("netconsole: network logging started\n");
 	} else {	/* false */
-		/* We need to disable the netconsole before cleaning it up
-		 * otherwise we might end up in write_msg() with
-		 * nt->np.dev == NULL and nt->enabled == true
-		 */
-		console_lock();
-		nt->enabled = false;
-		console_unlock();
-		netpoll_cleanup(&nt->np);
+		netconsole_disable(nt);
 	}
 
-	nt->enabled = enabled;
-
 	return strnlen(buf, count);
 }
 

@@ -633,13 +663,7 @@ static void drop_netconsole_target(struct config_group *group,
 	list_del(&nt->list);
 	console_unlock();
 
-	/*
-	 * The target may have never been enabled, or was manually disabled
-	 * before being removed so netpoll may have already been cleaned up.
-	 */
-	if (nt->enabled)
-		netpoll_cleanup(&nt->np);
-
+	netconsole_disable(nt);
 	config_item_put(&nt->item);
 	mutex_unlock(&netconsole_mutex);
 }

@@ -675,22 +699,16 @@ repeat:
 	to_disable = NULL;
 	console_lock();
 	list_for_each_entry(nt, &target_list, list) {
-		if (!nt->disable_scheduled)
-			continue;
-		nt->disable_scheduled = false;
-
-		if (!nt->enabled)
-			continue;
-
-		netconsole_target_get(nt);
-		nt->enabled = false;
-		to_disable = nt;
-		break;
+		if (nt->disable_scheduled) {
+			nt->disable_scheduled = false;
+			netconsole_target_get(nt);
+			to_disable = nt;
+		}
 	}
 	console_unlock();
 
 	if (to_disable) {
-		netpoll_cleanup(&to_disable->np);
+		netconsole_disable(to_disable);
 		netconsole_target_put(to_disable);
 		goto repeat;
 	}

@@ -795,10 +813,23 @@ static struct console netconsole = {
 	.write	= write_msg,
 };
 
+static void __init_or_module netconsole_destroy_all(void)
+{
+	struct netconsole_target *nt, *tmp;
+
+	lockdep_assert_held(&netconsole_mutex);
+
+	/* targets are already inactive, skipping the console lock is safe */
+	list_for_each_entry_safe(nt, tmp, &target_list, list) {
+		list_del(&nt->list);
+		netconsole_disable(nt);
+		kfree(nt);
+	}
+}
+
 static int __init init_netconsole(void)
 {
 	int err;
-	struct netconsole_target *nt, *tmp;
 	char *target_config;
 	char *input = config;
 

@@ -806,17 +837,9 @@ static int __init init_netconsole(void)
 
 	if (strnlen(input, MAX_PARAM_LENGTH)) {
 		while ((target_config = strsep(&input, ";"))) {
-			nt = alloc_param_target(target_config);
-			if (IS_ERR(nt)) {
-				err = PTR_ERR(nt);
+			err = create_param_target(target_config);
+			if (err)
 				goto fail;
-			}
-			/* Dump existing printks when we register */
-			netconsole.flags |= CON_PRINTBUFFER;
-
-			console_lock();
-			list_add(&nt->list, &target_list);
-			console_unlock();
 		}
 	}
 

@@ -838,12 +861,7 @@ undonotifier:
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);
 fail:
 	pr_err("cleaning up\n");
-
-	/* targets are already inactive, skipping the console lock is safe */
-	list_for_each_entry_safe(nt, tmp, &target_list, list) {
-		list_del(&nt->list);
-		free_param_target(nt);
-	}
+	netconsole_destroy_all();
 	mutex_unlock(&netconsole_mutex);
 	cancel_work_sync(&netconsole_deferred_disable_work);
 	return err;

@@ -851,19 +869,12 @@ fail:
 
 static void __exit cleanup_netconsole(void)
 {
-	struct netconsole_target *nt, *tmp;
-
 	mutex_lock(&netconsole_mutex);
 
 	unregister_console(&netconsole);
 	dynamic_netconsole_exit();
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);
-
-	/* targets are already inactive, skipping the console lock is safe */
-	list_for_each_entry_safe(nt, tmp, &target_list, list) {
-		list_del(&nt->list);
-		free_param_target(nt);
-	}
+	netconsole_destroy_all();
 
 	mutex_unlock(&netconsole_mutex);
 	cancel_work_sync(&netconsole_deferred_disable_work);

index d72d902..626d9f0 100644
@@ -83,6 +83,10 @@ static LIST_HEAD(target_list);
 /* protects target creation/destruction and enable/disable */
 static DEFINE_MUTEX(netconsole_mutex);
 
+static bool netconsole_ext_used_during_init;
+static bool netconsole_ext_registered;
+static struct console netconsole_ext;
+
 static struct console netconsole;
 
 /**

@@ -112,6 +116,7 @@ struct netconsole_target {
 #endif
 	bool			enabled;
 	bool			disable_scheduled;
+	bool			extended;
 	struct netpoll		np;
 };
 

@@ -194,6 +199,81 @@ static struct netconsole_target *alloc_netconsole_target(void)
 	return nt;
 }
 
+/**
+ * send_ext_msg_udp - send extended log message to target
+ * @nt: target to send message to
+ * @msg: extended log message to send
+ * @msg_len: length of message
+ *
+ * Transfer extended log @msg to @nt.  If @msg is too long, it'll be split
+ * and transmitted in multiple chunks with ncfrag header field added to
+ * enable correct reassembly.
+ */
+static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
+			     int msg_len)
+{
+	static char buf[MAX_PRINT_CHUNK];
+	const int max_extra_len = sizeof(",ncfrag=0000@00/00");
+	const char *header, *body;
+	int header_len = msg_len, body_len = 0;
+	int chunk_len, nr_chunks, i;
+
+	if (!nt->enabled || !netif_running(nt->np.dev))
+		return;
+
+	if (msg_len <= MAX_PRINT_CHUNK) {
+		netpoll_send_udp(&nt->np, msg, msg_len);
+		return;
+	}
+
+	/* need to insert extra header fields, detect header and body */
+	header = msg;
+	body = memchr(msg, ';', msg_len);
+	if (body) {
+		header_len = body - header;
+		body_len = msg_len - header_len - 1;
+		body++;
+	}
+
+	chunk_len = MAX_PRINT_CHUNK - header_len - max_extra_len;
+	if (WARN_ON_ONCE(chunk_len <= 0))
+		return;
+
+	/*
+	 * Transfer possibly multiple chunks with extra header fields.
+	 *
+	 * If @msg needs to be split to fit MAX_PRINT_CHUNK, add
+	 * "ncfrag=<byte-offset>@<0-based-chunk-index>/<total-chunks>" to
+	 * enable proper reassembly on receiver side.
+	 */
+	memcpy(buf, header, header_len);
+	nr_chunks = DIV_ROUND_UP(body_len, chunk_len);
+
+	for (i = 0; i < nr_chunks; i++) {
+		int this_header = header_len;
+		int this_chunk;
+
+		if (nr_chunks > 1)
+			this_header += scnprintf(buf + this_header,
+						 sizeof(buf) - this_header,
+						 ",ncfrag=%d@%d/%d",
+						 i * chunk_len, i, nr_chunks);
+		if (this_header < sizeof(buf))
+			buf[this_header++] = ';';
+
+		if (WARN_ON_ONCE(this_header + chunk_len > MAX_PRINT_CHUNK))
+			return;
+
+		this_chunk = min(body_len, chunk_len);
+		memcpy(buf + this_header, body, this_chunk);
+
+		netpoll_send_udp(&nt->np, buf, this_header + this_chunk);
+
+		body += this_chunk;
+		body_len -= this_chunk;
+	}
+}
+
 static int netconsole_enable(struct netconsole_target *nt)
 {
 	int err;

@@ -241,6 +321,11 @@ static int create_param_target(char *target_config)
 	if (!nt)
 		goto fail;
 
+	if (*target_config == '+') {
+		nt->extended = 1;
+		target_config++;
+	}
+
 	/* Parse parameters and setup netpoll */
 	err = netpoll_parse_options(&nt->np, target_config);
 	if (err)

@@ -255,7 +340,12 @@ static int create_param_target(char *target_config)
 		goto fail_del;
 
 	/* Dump existing printks when we register */
-	netconsole.flags |= CON_PRINTBUFFER;
+	if (nt->extended) {
+		netconsole_ext.flags |= CON_PRINTBUFFER;
+		netconsole_ext_used_during_init = true;
+	} else {
+		netconsole.flags |= CON_PRINTBUFFER;
+	}
 
 	return 0;
 

@@ -313,6 +403,11 @@ static ssize_t show_enabled(struct netconsole_target *nt, char *buf)
 	return snprintf(buf, PAGE_SIZE, "%d\n", nt->enabled);
 }
 
+static ssize_t show_extended(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%d\n", nt->extended);
+}
+
 static ssize_t show_dev_name(struct netconsole_target *nt, char *buf)
 {
 	return snprintf(buf, PAGE_SIZE, "%s\n", nt->np.dev_name);

@@ -401,6 +496,30 @@ static ssize_t store_enabled(struct netconsole_target *nt,
 	return strnlen(buf, count);
 }
 
+static ssize_t store_extended(struct netconsole_target *nt,
+			      const char *buf,
+			      size_t count)
+{
+	int extended;
+	int err;
+
+	if (nt->enabled) {
+		pr_err("target (%s) is enabled, disable to update parameters\n",
+		       config_item_name(&nt->item));
+		return -EINVAL;
+	}
+
+	err = kstrtoint(buf, 10, &extended);
+	if (err < 0)
+		return err;
+	if (extended < 0 || extended > 1)
+		return -EINVAL;
+
+	nt->extended = extended;
+
+	return strnlen(buf, count);
+}
+
 static ssize_t store_dev_name(struct netconsole_target *nt,
 			      const char *buf,
 			      size_t count)

@@ -553,6 +672,7 @@ static struct netconsole_target_attr netconsole_target_##_name =	\
 	__CONFIGFS_ATTR(_name, S_IRUGO | S_IWUSR, show_##_name, store_##_name)
 
 NETCONSOLE_TARGET_ATTR_RW(enabled);
+NETCONSOLE_TARGET_ATTR_RW(extended);
 NETCONSOLE_TARGET_ATTR_RW(dev_name);
 NETCONSOLE_TARGET_ATTR_RW(local_port);
 NETCONSOLE_TARGET_ATTR_RW(remote_port);

@@ -563,6 +683,7 @@ NETCONSOLE_TARGET_ATTR_RW(remote_mac);
 
 static struct configfs_attribute *netconsole_target_attrs[] = {
 	&netconsole_target_enabled.attr,
+	&netconsole_target_extended.attr,
 	&netconsole_target_dev_name.attr,
 	&netconsole_target_local_port.attr,
 	&netconsole_target_remote_port.attr,

@@ -645,9 +766,16 @@ static struct config_item *make_netconsole_target(struct config_group *group,
 
 	/* Adding, but it is disabled */
 	mutex_lock(&netconsole_mutex);
+
 	console_lock();
 	list_add(&nt->list, &target_list);
 	console_unlock();
+
+	if (nt->extended && !netconsole_ext_registered) {
+		register_console(&netconsole_ext);
+		netconsole_ext_registered = true;
+	}
+
 	mutex_unlock(&netconsole_mutex);
 
 	return &nt->item;

@@ -776,6 +904,19 @@ static struct notifier_block netconsole_netdev_notifier = {
 	.notifier_call  = netconsole_netdev_event,
 };
 
+static void write_ext_msg(struct console *con, const char *msg,
+			  unsigned int len)
+{
+	struct netconsole_target *nt;
+
+	if ((oops_only && !oops_in_progress) || list_empty(&target_list))
+		return;
+
+	list_for_each_entry(nt, &target_list, list)
+		if (nt->extended)
+			send_ext_msg_udp(nt, msg, len);
+}
+
 static void write_msg(struct console *con, const char *msg, unsigned int len)
 {
 	int frag, left;

@@ -789,6 +930,8 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 		return;
 
 	list_for_each_entry(nt, &target_list, list) {
+		if (nt->extended)
+			continue;
 		if (nt->enabled && netif_running(nt->np.dev)) {
 			/*
 			 * We nest this inside the for-each-target loop above

@@ -807,6 +950,12 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 	}
 }
 
+static struct console netconsole_ext = {
+	.name	= "netcon_ext",
+	.flags	= CON_ENABLED | CON_EXTENDED,
+	.write	= write_ext_msg,
+};
+
 static struct console netconsole = {
 	.name	= "netcon",
 	.flags	= CON_ENABLED,

@@ -851,6 +1000,11 @@ static int __init init_netconsole(void)
 	if (err)
 		goto undonotifier;
 
+	if (netconsole_ext_used_during_init) {
+		register_console(&netconsole_ext);
+		netconsole_ext_registered = true;
+	}
+
 	register_console(&netconsole);
 	pr_info("network logging started\n");
 

@@ -871,6 +1025,9 @@ static void __exit cleanup_netconsole(void)
 {
 	mutex_lock(&netconsole_mutex);
 
+	if (netconsole_ext_registered)
+		unregister_console(&netconsole_ext);
+
 	unregister_console(&netconsole);
 	dynamic_netconsole_exit();
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);

index 626d9f0..b2763e0 100644
@@ -45,7 +45,10 @@
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/netpoll.h>
+#include <linux/net.h>
 #include <linux/inet.h>
+#include <linux/file.h>
+#include <linux/poll.h>
 #include <linux/configfs.h>
 #include <linux/etherdevice.h>
 

@@ -89,6 +92,14 @@ static struct console netconsole_ext;
 
 static struct console netconsole;
 
+union sockaddr_in46 {
+	struct sockaddr		addr;
+	struct sockaddr_in6	in6;
+	struct sockaddr_in	in4;
+};
+
+static char *netconsole_ext_tx_buf;	/* CONSOLE_EXT_LOG_MAX */
+
 /**
  * struct netconsole_target - Represents a configured netconsole target.
  * @list:	Links this target into the target_list.

@@ -118,6 +129,14 @@ struct netconsole_target {
 	bool			disable_scheduled;
 	bool			extended;
 	struct netpoll		np;
+
+	/* response packet handling for extended netconsoles */
+	union sockaddr_in46	raddr;		/* logging target address */
+	struct file		*rx_file;	/* sock to receive responses */
+	poll_table		rx_ptable;	/* for polling the socket */
+	wait_queue_t		rx_wait;	/* ditto */
+	wait_queue_head_t	*rx_waitq;	/* ditto */
+	struct work_struct	rx_work;	/* receive & process packets */
 };
 
 #ifdef	CONFIG_NETCONSOLE_DYNAMIC

@@ -274,6 +293,219 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
 	}
 }
 
+static bool sockaddr_in46_equal(union sockaddr_in46 *a, union sockaddr_in46 *b)
+{
+	if (a->addr.sa_family != b->addr.sa_family)
+		return false;
+	if (a->in4.sin_port != b->in4.sin_port)
+		return false;
+	if (a->addr.sa_family == AF_INET &&
+	    memcmp(&a->in4.sin_addr, &b->in4.sin_addr, sizeof(a->in4.sin_addr)))
+		return false;
+	if (a->addr.sa_family == AF_INET6 &&
+	    memcmp(&a->in6.sin6_addr, &b->in6.sin6_addr, sizeof(a->in6.sin6_addr)))
+		return false;
+	return true;
+}
+
+/**
+ * netconsole_rx_work_fn - work function to handle netconsole ack packets
+ * @work: netconsole_target->rx_work
+ *
+ * This function is scheduled when packets are received on the source port
+ * of extended netconsole target and responds to ack messages from the
+ * remote logger.  An ack message has the following format.
+ *
+ * nca <missing-seq> <missing-seq> ...
+ *
+ * There can be any number of missing-seq's as long as the whole payload
+ * fits inside MAX_PRINT_CHUNK.  This function re-transmits each message
+ * matching the missing-seq's if available.  This can be used to implement
+ * reliable logging from the receiver side.
+ *
+ * The rx path doesn't interfere with the normal tx path except for when it
+ * actually sends out the messages, and that path doesn't depend on
+ * anything more working compared to the normal tx path.  As such, this
+ * shouldn't make netconsole any less robust when things start going south.
+ */
+static void netconsole_rx_work_fn(struct work_struct *work)
+{
+	struct netconsole_target *nt =
+		container_of(work, struct netconsole_target, rx_work);
+	union sockaddr_in46 raddr;
+	struct msghdr msgh = { .msg_name = &raddr.addr, };
+	struct kvec iov;
+	char *tx_buf = netconsole_ext_tx_buf;
+	char *rx_buf, *pos, *tok;
+	u64 seq;
+	int len;
+
+	rx_buf = kmalloc(MAX_PRINT_CHUNK + 1, GFP_KERNEL);
+	if (!rx_buf && printk_ratelimit()) {
+		pr_warning("failed to allocate RX buffer\n");
+		return;
+	}
+
+	iov.iov_base = rx_buf;
+	iov.iov_len = MAX_PRINT_CHUNK;
+repeat:
+	msgh.msg_namelen = sizeof(raddr);
+	len = kernel_recvmsg(sock_from_file(nt->rx_file, &len), &msgh, &iov, 1,
+			     MAX_PRINT_CHUNK, MSG_DONTWAIT);
+	if (len < 0) {
+		if (len != -EAGAIN && printk_ratelimit())
+			pr_warning("RX failed err=%d\n", len);
+		kfree(rx_buf);
+		return;
+	}
+
+	if (!sockaddr_in46_equal(msgh.msg_name, &nt->raddr)) {
+		if (printk_ratelimit())
+			pr_warning("stray packet from %pIS:%u\n",
+				   &raddr.addr, ntohs(raddr.in4.sin_port));
+		goto repeat;
+	}
+
+	rx_buf[len] = '\0';
+	pos = rx_buf;
+	tok = strsep(&pos, " ");
+
+	/* nca header */
+	if (strncmp(tok, "nca", 3)) {
+		if (printk_ratelimit())
+			pr_warning("malformed packet from %pIS:%u\n",
+				   &nt->raddr, ntohs(nt->raddr.in4.sin_port));
+		goto repeat;
+	}
+	tok += 3;
+
+	console_lock();
+
+	/* <missing-seq>... */
+	while ((tok = strsep(&pos, " "))) {
+		if (sscanf(tok, "%llu", &seq)) {
+			len = ext_log_from_seq(tx_buf, CONSOLE_EXT_LOG_MAX, seq);
+			if (len >= 0)
+				send_ext_msg_udp(nt, tx_buf, len);
+		}
+	}
+
+	console_unlock();
+	goto repeat;
+}
+
+static int netconsole_rx_wait_fn(wait_queue_t *wait, unsigned mode, int flags,
+				 void *key)
+{
+	struct netconsole_target *nt =
+		container_of(wait, struct netconsole_target, rx_wait);
+
+	schedule_work(&nt->rx_work);
+	return 0;
+}
+
+static void netconsole_rx_ptable_queue_fn(struct file *file,
+					  wait_queue_head_t *waitq,
+					  poll_table *ptable)
+{
+	struct netconsole_target *nt =
+		container_of(ptable, struct netconsole_target, rx_ptable);
+
+	nt->rx_waitq = waitq;
+	add_wait_queue(waitq, &nt->rx_wait);
+}
+
+static void netconsole_enable_rx(struct netconsole_target *nt)
+{
+	union sockaddr_in46 laddr = { }, raddr = { };
+	struct socket *sock;
+	struct file *file;
+	int addr_len, ret;
+
+	if (!netconsole_ext_tx_buf) {
+		char *buf;
+
+		buf = kmalloc(CONSOLE_EXT_LOG_MAX, GFP_KERNEL);
+		if (!buf) {
+			kfree(buf);
+			pr_warning("failed to allocate TX buffer\n");
+			return;
+		}
+
+		if (cmpxchg(&netconsole_ext_tx_buf, NULL, buf))
+			kfree(buf);
+	}
+
+	if (!nt->np.ipv6) {
+		laddr.in4.sin_family = AF_INET;
+		laddr.in4.sin_port = htons(nt->np.local_port);
+		laddr.in4.sin_addr = nt->np.local_ip.in;
+		raddr.in4.sin_family = AF_INET;
+		raddr.in4.sin_port = htons(nt->np.remote_port);
+		raddr.in4.sin_addr = nt->np.remote_ip.in;
+		addr_len = sizeof(laddr.in4);
+	} else {
+		laddr.in6.sin6_family = AF_INET6;
+		laddr.in6.sin6_port = htons(nt->np.local_port);
+		laddr.in6.sin6_addr = nt->np.local_ip.in6;
+		raddr.in6.sin6_family = AF_INET6;
+		raddr.in6.sin6_port = htons(nt->np.remote_port);
+		raddr.in6.sin6_addr = nt->np.remote_ip.in6;
+		addr_len = sizeof(laddr.in6);
+	}
+
+	ret = sock_create_kern(laddr.addr.sa_family, SOCK_DGRAM, IPPROTO_UDP,
+			       &sock);
+	if (ret) {
+		pr_warning("failed to create rx socket, err=%d\n", ret);
+		return;
+	}
+
+	file = sock_alloc_file(sock, 0, NULL);
+	if (IS_ERR(file)) {
+		pr_warning("failed to rx socket file, err=%ld\n", PTR_ERR(file));
+		sock_release(sock);
+		return;
+	}
+
+	ret = sock->ops->bind(sock, &laddr.addr, addr_len);
+	if (ret) {
+		pr_warning("failed to bind rx socket at %pIS:%u, err=%d\n",
+			   &laddr.addr, ntohs(laddr.in4.sin_port), ret);
+		fput(file);
+		return;
+	}
+
+	nt->raddr = raddr;
+	init_poll_funcptr(&nt->rx_ptable, netconsole_rx_ptable_queue_fn);
+	init_waitqueue_func_entry(&nt->rx_wait, netconsole_rx_wait_fn);
+	INIT_WORK(&nt->rx_work, netconsole_rx_work_fn);
+
+	ret = file->f_op->poll(file, &nt->rx_ptable);
+	if (ret < 0) {
+		pr_warning("failed to poll rx socket, err=%d\n", ret);
+		fput(file);
+		return;
+	}
+
+	if (ret & POLLIN)
+		schedule_work(&nt->rx_work);
+
+	nt->rx_file = file;
+}
+
+static void netconsole_disable_rx(struct netconsole_target *nt)
+{
+	if (!nt->rx_file)
+		return;
+
+	remove_wait_queue(nt->rx_waitq, &nt->rx_wait);
+	cancel_work_sync(&nt->rx_work);
+
+	fput(nt->rx_file);
+	nt->rx_file = NULL;
+}
+
 static int netconsole_enable(struct netconsole_target *nt)
 {
 	int err;

@@ -285,6 +517,9 @@ static int netconsole_enable(struct netconsole_target *nt)
 	if (err)
 		return err;
 
+	if (nt->extended)
+		netconsole_enable_rx(nt);
+
 	console_lock();
 	nt->enabled = true;
 	console_unlock();

@@ -305,6 +540,7 @@ static void netconsole_disable(struct netconsole_target *nt)
 		nt->enabled = false;
 		console_unlock();
 
+		netconsole_disable_rx(nt);
 		netpoll_cleanup(&nt->np);
 	}
 }

@@ -974,6 +1210,8 @@ static void __init_or_module netconsole_destroy_all(void)
 		netconsole_disable(nt);
 		kfree(nt);
 	}
+
+	kfree(netconsole_ext_tx_buf);
 }
 
 static int __init init_netconsole(void)

index b2763e0..82c8be0 100644
@@ -49,6 +49,7 @@
 #include <linux/inet.h>
 #include <linux/file.h>
 #include <linux/poll.h>
+#include <linux/timer.h>
 #include <linux/configfs.h>
 #include <linux/etherdevice.h>
 

@@ -59,6 +60,10 @@ MODULE_LICENSE("GPL");
 #define MAX_PARAM_LENGTH	256
 #define MAX_PRINT_CHUNK		1000
 
+#define ACK_TIMEOUT		(10 * HZ)
+#define EMG_TX_MIN_INTV		(HZ / 10)
+#define EMG_TX_MAX_INTV		HZ
+
 static char config[MAX_PARAM_LENGTH];
 module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0);
 MODULE_PARM_DESC(netconsole, " netconsole=[src-port]@[src-ip]/[dev],[tgt-port]@<tgt-ip>/[tgt-macaddr]");

@@ -137,6 +142,13 @@ struct netconsole_target {
 	wait_queue_t		rx_wait;	/* ditto */
 	wait_queue_head_t	*rx_waitq;	/* ditto */
 	struct work_struct	rx_work;	/* receive & process packets */
+
+	/* ack handling and emergency transmission for extended netconsoles */
+	unsigned long		ack_tstmp;	/* pending ack timestamp */
+	u64			ack_seq;	/* last acked sequence */
+	struct timer_list	ack_timer;	/* ack timeout */
+	unsigned long		emg_tx_intv;	/* emergency tx interval */
+	u64			emg_tx_seq;	/* current emg tx sequence */
 };
 
 #ifdef	CONFIG_NETCONSOLE_DYNAMIC

@@ -223,16 +235,17 @@ static struct netconsole_target *alloc_netconsole_target(void)
  * @nt: target to send message to
  * @msg: extended log message to send
  * @msg_len: length of message
+ * @emg_tx: is it for emergency transmission?
  *
  * Transfer extended log @msg to @nt.  If @msg is too long, it'll be split
  * and transmitted in multiple chunks with ncfrag header field added to
- * enable correct reassembly.
+ * enable correct reassembly.  If @emg_tx, emg header field is added.
  */
 static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
-			     int msg_len)
+			     int msg_len, bool emg_tx)
 {
 	static char buf[MAX_PRINT_CHUNK];
-	const int max_extra_len = sizeof(",ncfrag=0000@00/00");
+	const int max_extra_len = sizeof(",emg=1,ncfrag=0000@00/00");
 	const char *header, *body;
 	int header_len = msg_len, body_len = 0;
 	int chunk_len, nr_chunks, i;

@@ -240,7 +253,7 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
 	if (!nt->enabled || !netif_running(nt->np.dev))
 		return;
 
-	if (msg_len <= MAX_PRINT_CHUNK) {
+	if (!emg_tx && msg_len <= MAX_PRINT_CHUNK) {
 		netpoll_send_udp(&nt->np, msg, msg_len);
 		return;
 	}

@@ -261,6 +274,8 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
 	/*
 	 * Transfer possibly multiple chunks with extra header fields.
 	 *
+	 * For emergency transfers due to missing acks, add "emg=1".
+	 *
 	 * If @msg needs to be split to fit MAX_PRINT_CHUNK, add
 	 * "ncfrag=<byte-offset>@<0-based-chunk-index>/<total-chunks>" to
 	 * enable proper reassembly on receiver side.

@@ -272,6 +287,10 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
 		int this_header = header_len;
 		int this_chunk;
 
+		if (emg_tx)
+			this_header += scnprintf(buf + this_header,
+						 sizeof(buf) - this_header,
+						 ",emg=1");
 		if (nr_chunks > 1)
 			this_header += scnprintf(buf + this_header,
 						 sizeof(buf) - this_header,

@@ -309,6 +328,78 @@ static bool sockaddr_in46_equal(union sockaddr_in46 *a, union sockaddr_in46 *b)
 }
 
 /**
+ * netconsole_ack_timer_fn - timer function to handle netconsole ack timeouts
+ * @data: netconsole_target
+ *
+ * For an extended netconsole, if the remote logger acked messages
+ * previously but is failing to ack new messages for over ACK_TIMEOUT, this
+ * timer kicks in for emergency transmission.
+ *
+ * The lack of ack may be caused by a number of things including the ack
+ * packet being dropped or the network stack oopsing.  Whatever the cause
+ * may be, we repeatedly retransmit the unacked message at increasing
+ * interval which should allow the remote logger to eventually obtain all
+ * messages as long as the packets are going out.
+ *
+ * This mechanism depends only on the timer and netpoll working.
+ */
+static void netconsole_ack_timer_fn(unsigned long data)
+{
+	struct netconsole_target *nt = (void *)data;
+	unsigned long now = jiffies;
+	unsigned long next_at;
+	char *buf = netconsole_ext_tx_buf;
+	u64 begin_seq, end_seq, seq;
+	int len;
+
+	if (!console_trylock()) {
+		mod_timer(&nt->ack_timer, now + 1);
+		return;
+	}
+
+	log_seq_range(&begin_seq, &end_seq);
+	if (nt->ack_seq == end_seq - 1) {
+		nt->ack_tstmp = 0;
+		next_at = now + ACK_TIMEOUT;
+		goto out_unlock;
+	}
+	if (time_before(now, nt->ack_tstmp + ACK_TIMEOUT)) {
+		next_at = nt->ack_tstmp + ACK_TIMEOUT;
+		goto out_unlock;
+	}
+
+	/* zero emg_tx_intv indicates that we're starting emergency tx */
+	if (!nt->emg_tx_intv) {
+		nt->emg_tx_intv = EMG_TX_MIN_INTV;
+		nt->emg_tx_seq = nt->ack_seq + 1;
+	}
+
+	seq = nt->emg_tx_seq;
+	do {
+		len = ext_log_from_seq(buf, CONSOLE_EXT_LOG_MAX, seq);
+	} while (len < 0 && ++seq < end_seq);
+
+	if (len >= 0) {
+		send_ext_msg_udp(nt, buf, len, true);
+		seq++;
+	}
+
+	nt->emg_tx_seq = seq;
+
+	if (nt->emg_tx_seq >= end_seq) {
+		/* all messages transferred, bump up intv and repeat */
+		nt->emg_tx_intv = min_t(unsigned long, 2 * nt->emg_tx_intv,
+					EMG_TX_MAX_INTV);
+		nt->emg_tx_seq = nt->ack_seq + 1;
+	}
+
+	next_at = now + nt->emg_tx_intv;
+out_unlock:
+	console_unlock();
+	mod_timer(&nt->ack_timer, next_at);
+}
+
+/**
  * netconsole_rx_work_fn - work function to handle netconsole ack packets
  * @work: netconsole_target->rx_work
  *

@@ -316,7 +407,7 @@ static bool sockaddr_in46_equal(union sockaddr_in46 *a, union sockaddr_in46 *b)
  * of extended netconsole target and responds to ack messages from the
  * remote logger.  An ack message has the following format.
  *
- * nca <missing-seq> <missing-seq> ...
+ * nca[<ack-seq>] <missing-seq> <missing-seq> ...
  *
  * There can be any number of missing-seq's as long as the whole payload
  * fits inside MAX_PRINT_CHUNK.  This function re-transmits each message

@@ -327,6 +418,10 @@ static bool sockaddr_in46_equal(union sockaddr_in46 *a, union sockaddr_in46 *b)
  * actually sends out the messages, and that path doesn't depend on
  * anything more working compared to the normal tx path.  As such, this
  * shouldn't make netconsole any less robust when things start going south.
+ *
+ * If <ack-seq> exists, emergency tx is enabled.  Whenever ack is lagging
+ * by more than ACK_TIMEOUT, netconsole will repeatedly send out unacked
+ * messages with increasing interval.  See netconsole_ack_timer_fn().
  */
 static void netconsole_rx_work_fn(struct work_struct *work)
 {

@@ -335,6 +430,7 @@ static void netconsole_rx_work_fn(struct work_struct *work)
 	union sockaddr_in46 raddr;
 	struct msghdr msgh = { .msg_name = &raddr.addr, };
 	struct kvec iov;
+	bool ack_was_enabled = nt->ack_seq;
 	char *tx_buf = netconsole_ext_tx_buf;
 	char *rx_buf, *pos, *tok;
 	u64 seq;

@@ -355,6 +451,9 @@ repeat:
 	if (len < 0) {
 		if (len != -EAGAIN && printk_ratelimit())
 			pr_warning("RX failed err=%d\n", len);
+		if (!ack_was_enabled && nt->ack_seq)
+			pr_info("ACK timeout enabled for %pIS:%d\n",
+				&nt->raddr.addr, ntohs(nt->raddr.in4.sin_port));
 		kfree(rx_buf);
 		return;
 	}

@@ -381,12 +480,25 @@ repeat:
 
 	console_lock();
 
+	/* <ack-seq> */
+	if (sscanf(tok, "%llu", &seq)) {
+		u64 begin_seq, end_seq;
+
+		log_seq_range(&begin_seq, &end_seq);
+		if (seq && seq < end_seq) {
+			nt->ack_seq = max(seq, nt->ack_seq);
+			nt->emg_tx_intv = 0;
+			if (!ack_was_enabled)
+				mod_timer(&nt->ack_timer, jiffies);
+		}
+	}
+
 	/* <missing-seq>... */
 	while ((tok = strsep(&pos, " "))) {
 		if (sscanf(tok, "%llu", &seq)) {
 			len = ext_log_from_seq(tx_buf, CONSOLE_EXT_LOG_MAX, seq);
 			if (len >= 0)
-				send_ext_msg_udp(nt, tx_buf, len);
+				send_ext_msg_udp(nt, tx_buf, len, false);
 		}
 	}
 

@@ -480,6 +592,7 @@ static void netconsole_enable_rx(struct netconsole_target *nt)
 	init_poll_funcptr(&nt->rx_ptable, netconsole_rx_ptable_queue_fn);
 	init_waitqueue_func_entry(&nt->rx_wait, netconsole_rx_wait_fn);
 	INIT_WORK(&nt->rx_work, netconsole_rx_work_fn);
+	setup_timer(&nt->ack_timer, netconsole_ack_timer_fn, (unsigned long)nt);
 
 	ret = file->f_op->poll(file, &nt->rx_ptable);
 	if (ret < 0) {

@@ -501,6 +614,7 @@ static void netconsole_disable_rx(struct netconsole_target *nt)
 
 	remove_wait_queue(nt->rx_waitq, &nt->rx_wait);
 	cancel_work_sync(&nt->rx_work);
+	del_timer_sync(&nt->ack_timer);
 
 	fput(nt->rx_file);
 	nt->rx_file = NULL;

@@ -1148,9 +1262,13 @@ static void write_ext_msg(struct console *con, const char *msg,
 	if ((oops_only && !oops_in_progress) || list_empty(&target_list))
 		return;
 
-	list_for_each_entry(nt, &target_list, list)
-		if (nt->extended)
-			send_ext_msg_udp(nt, msg, len);
+	list_for_each_entry(nt, &target_list, list) {
+		if (nt->extended) {
+			send_ext_msg_udp(nt, msg, len, false);
+			if (!nt->ack_tstmp)
+				nt->ack_tstmp = jiffies ?: 1;
+		}
+	}
 }
 
 static void write_msg(struct console *con, const char *msg, unsigned int len)

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