v6.7-rc5-rt5

index ba6de401c458e..6b89e9c2374a5 100644
@@ -617,9 +617,18 @@ static bool univ8250_console_write_thread(struct console *co,
 	return serial8250_console_write_thread(up, wctxt);
 }
 
-static struct uart_port *univ8250_console_uart_port(struct console *con)
+static void univ8250_console_driver_enter(struct console *con, unsigned long *flags)
 {
-	return &serial8250_ports[con->index].port;
+	struct uart_port *up = &serial8250_ports[con->index].port;
+
+	__uart_port_lock_irqsave(up, flags);
+}
+
+static void univ8250_console_driver_exit(struct console *con, unsigned long flags)
+{
+	struct uart_port *up = &serial8250_ports[con->index].port;
+
+	__uart_port_unlock_irqrestore(up, flags);
 }
 #endif /* CONFIG_SERIAL_8250_LEGACY_CONSOLE */
 

@@ -727,8 +736,9 @@ static struct console univ8250_console = {
 #else
 	.write_atomic	= univ8250_console_write_atomic,
 	.write_thread	= univ8250_console_write_thread,
+	.driver_enter	= univ8250_console_driver_enter,
+	.driver_exit	= univ8250_console_driver_exit,
 	.flags		= CON_PRINTBUFFER | CON_ANYTIME | CON_NBCON,
-	.uart_port	= univ8250_console_uart_port,
 #endif
 	.device		= uart_console_device,
 	.setup		= univ8250_console_setup,

index c8d15f659de98..3b26105f01570 100644
@@ -3509,13 +3509,11 @@ bool serial8250_console_write_thread(struct uart_8250_port *up,
 	if (!nbcon_enter_unsafe(wctxt))
 		return false;
 
-	/*
-	 *	First save the IER then disable the interrupts
-	 */
+	/* First save IER then disable the interrupts. */
 	ier = serial_port_in(port, UART_IER);
 	serial8250_clear_IER(up);
 
-	/* check scratch reg to see if port powered off during system sleep */
+	/* Check scratch reg if port powered off during system sleep. */
 	if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) {
 		serial8250_console_restore(up);
 		up->canary = 0;

@@ -3563,30 +3561,25 @@ bool serial8250_console_write_thread(struct uart_8250_port *up,
 	while (!nbcon_enter_unsafe(wctxt))
 		nbcon_reacquire(wctxt);
 
-	/*
-	 *	Finally, wait for transmitter to become empty
-	 *	and restore the IER
-	 */
+	/* Finally, wait for transmitter to become empty and restore IER. */
 	wait_for_xmitr(up, UART_LSR_BOTH_EMPTY);
-
 	if (em485) {
 		mdelay(port->rs485.delay_rts_after_send);
 		if (em485->tx_stopped)
 			up->rs485_stop_tx(up);
 	}
-
 	serial_port_out(port, UART_IER, ier);
 
 	/*
-	 *	The receive handling will happen properly because the
-	 *	receive ready bit will still be set; it is not cleared
-	 *	on read.  However, modem control will not, we must
-	 *	call it if we have saved something in the saved flags
-	 *	while processing with interrupts off.
+	 * The receive handling will happen properly because the receive ready
+	 * bit will still be set; it is not cleared on read.  However, modem
+	 * control will not, we must call it if we have saved something in the
+	 * saved flags while processing with interrupts off.
 	 */
 	if (up->msr_saved_flags)
 		serial8250_modem_status(up);
 
+	/* Success if no handover/takeover and message fully printed. */
 	return (nbcon_exit_unsafe(wctxt) && done);
 }
 

@@ -3606,12 +3599,14 @@ bool serial8250_console_write_atomic(struct uart_8250_port *up,
 		return false;
 
 	/*
-	 *	First save the IER then disable the interrupts
+	 * First save IER then disable the interrupts. The special variant to
+	 * clear IER is used because atomic printing may occur without holding
+	 * the port lock.
 	 */
 	ier = serial_port_in(port, UART_IER);
 	__serial8250_clear_IER(up);
 
-	/* check scratch reg to see if port powered off during system sleep */
+	/* Check scratch reg if port powered off during system sleep. */
 	if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) {
 		serial8250_console_restore(up);
 		up->canary = 0;

@@ -3621,14 +3616,11 @@ bool serial8250_console_write_atomic(struct uart_8250_port *up,
 		uart_console_write(port, "\n", 1, serial8250_console_putchar);
 	uart_console_write(port, wctxt->outbuf, wctxt->len, serial8250_console_putchar);
 
-	/*
-	 *	Finally, wait for transmitter to become empty
-	 *	and restore the IER
-	 */
+	/* Finally, wait for transmitter to become empty and restore IER. */
 	wait_for_xmitr(up, UART_LSR_BOTH_EMPTY);
-
 	serial_port_out(port, UART_IER, ier);
 
+	/* Success if no handover/takeover. */
 	return nbcon_exit_unsafe(wctxt);
 }
 #endif /* CONFIG_SERIAL_8250_LEGACY_CONSOLE */

index ac14ff49e86bb..79ef2fd2bd155 100644
@@ -306,7 +306,8 @@ struct nbcon_write_context {
  *
  * @write_atomic:	Write callback for atomic context
  * @write_thread:	Write callback for non-atomic context
- * @uart_port:		Callback to provide the associated uart port
+ * @driver_enter:	Callback to begin synchronization with driver code
+ * @driver_exit:	Callback to finish synchronization with driver code
  * @nbcon_state:	State for nbcon consoles
  * @nbcon_seq:		Sequence number of the next record for nbcon to print
  * @pbufs:		Pointer to nbcon private buffer

@@ -339,7 +340,8 @@ struct console {
 						struct nbcon_write_context *wctxt);
 	bool			(*write_thread)(struct console *con,
 						struct nbcon_write_context *wctxt);
-	struct uart_port *	(*uart_port)(struct console *con);
+	void			(*driver_enter)(struct console *con, unsigned long *flags);
+	void			(*driver_exit)(struct console *con, unsigned long flags);
 	atomic_t		__private nbcon_state;
 	atomic_long_t		__private nbcon_seq;
 	struct printk_buffers	*pbufs;

index 196a4cf3ccb76..7a942e987b165 100644
@@ -197,8 +197,9 @@ void show_regs_print_info(const char *log_lvl);
 extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold;
 extern asmlinkage void dump_stack(void) __cold;
 void printk_trigger_flush(void);
-extern void nbcon_handle_port_lock(struct uart_port *up);
-extern void nbcon_handle_port_unlock(struct uart_port *up);
+void printk_legacy_allow_panic_sync(void);
+extern void nbcon_acquire(struct uart_port *up);
+extern void nbcon_release(struct uart_port *up);
 void nbcon_atomic_flush_unsafe(void);
 #else
 static inline __printf(1, 0)

@@ -280,11 +281,15 @@ static inline void printk_trigger_flush(void)
 {
 }
 
-static inline void nbcon_handle_port_lock(struct uart_port *up)
+static inline void printk_legacy_allow_panic_sync(void)
 {
 }
 
-static inline void nbcon_handle_port_unlock(struct uart_port *up)
+static inline void nbcon_acquire(struct uart_port *up)
+{
+}
+
+static inline void nbcon_release(struct uart_port *up)
 {
 }
 

index 198d8088a9984..a49ce4bf7fae8 100644
@@ -595,7 +595,7 @@ struct uart_port {
 static inline void uart_port_lock(struct uart_port *up)
 {
 	spin_lock(&up->lock);
-	nbcon_handle_port_lock(up);
+	nbcon_acquire(up);
 }
 
 /**

@@ -605,7 +605,7 @@ static inline void uart_port_lock(struct uart_port *up)
 static inline void uart_port_lock_irq(struct uart_port *up)
 {
 	spin_lock_irq(&up->lock);
-	nbcon_handle_port_lock(up);
+	nbcon_acquire(up);
 }
 
 /**

@@ -616,7 +616,7 @@ static inline void uart_port_lock_irq(struct uart_port *up)
 static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
 {
 	spin_lock_irqsave(&up->lock, *flags);
-	nbcon_handle_port_lock(up);
+	nbcon_acquire(up);
 }
 
 /**

@@ -630,7 +630,7 @@ static inline bool uart_port_trylock(struct uart_port *up)
 	if (!spin_trylock(&up->lock))
 		return false;
 
-	nbcon_handle_port_lock(up);
+	nbcon_acquire(up);
 	return true;
 }
 

@@ -646,7 +646,7 @@ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long
 	if (!spin_trylock_irqsave(&up->lock, *flags))
 		return false;
 
-	nbcon_handle_port_lock(up);
+	nbcon_acquire(up);
 	return true;
 }
 

@@ -656,7 +656,7 @@ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long
  */
 static inline void uart_port_unlock(struct uart_port *up)
 {
-	nbcon_handle_port_unlock(up);
+	nbcon_release(up);
 	spin_unlock(&up->lock);
 }
 

@@ -666,7 +666,7 @@ static inline void uart_port_unlock(struct uart_port *up)
  */
 static inline void uart_port_unlock_irq(struct uart_port *up)
 {
-	nbcon_handle_port_unlock(up);
+	nbcon_release(up);
 	spin_unlock_irq(&up->lock);
 }
 

@@ -677,7 +677,19 @@ static inline void uart_port_unlock_irq(struct uart_port *up)
  */
 static inline void uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
 {
-	nbcon_handle_port_unlock(up);
+	nbcon_release(up);
+	spin_unlock_irqrestore(&up->lock, flags);
+}
+
+/* Only for use in the console->driver_enter() callback. */
+static inline void __uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
+{
+	spin_lock_irqsave(&up->lock, *flags);
+}
+
+/* Only for use in the console->driver_exit() callback. */
+static inline void __uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
+{
 	spin_unlock_irqrestore(&up->lock, flags);
 }
 

index 88902355600f5..9fa44bc38f466 100644
@@ -370,6 +370,8 @@ void panic(const char *fmt, ...)
 	 */
 	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
 
+	printk_legacy_allow_panic_sync();
+
 	panic_print_sys_info(false);
 
 	kmsg_dump(KMSG_DUMP_PANIC);

@@ -447,6 +449,12 @@ void panic(const char *fmt, ...)
 	/* Do not scroll important messages printed above */
 	suppress_printk = 1;
 
+	/*
+	 * The final messages may not have been printed if in a context that
+	 * defers printing (such as NMI) and irq_work is not available.
+	 * Explicitly flush the kernel log buffer one last time.
+	 */
+	console_flush_on_panic(CONSOLE_FLUSH_PENDING);
 	nbcon_atomic_flush_unsafe();
 
 	local_irq_enable();

index a3ae0710346cd..7db6992c54f38 100644
@@ -82,6 +82,8 @@ void defer_console_output(void);
 
 u16 printk_parse_prefix(const char *text, int *level,
 			enum printk_info_flags *flags);
+void console_lock_spinning_enable(void);
+int console_lock_spinning_disable_and_check(int cookie);
 
 u64 nbcon_seq_read(struct console *con);
 void nbcon_seq_force(struct console *con, u64 seq);

@@ -90,7 +92,7 @@ void nbcon_init(struct console *con);
 void nbcon_free(struct console *con);
 enum nbcon_prio nbcon_get_default_prio(void);
 void nbcon_atomic_flush_all(void);
-bool nbcon_atomic_emit_next_record(struct console *con);
+bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, int cookie);
 void nbcon_kthread_create(struct console *con);
 void nbcon_wake_threads(void);
 void nbcon_legacy_kthread_create(void);

@@ -143,7 +145,7 @@ static inline void nbcon_kthread_wake(struct console *con)
 	 * Guarantee any new records can be seen by tasks preparing to wait
 	 * before this context checks if the rcuwait is empty.
 	 *
-	 * The full memory barrier in rcuwait_wake_up()  pairs with the full
+	 * The full memory barrier in rcuwait_wake_up() pairs with the full
 	 * memory barrier within set_current_state() of
 	 * ___rcuwait_wait_event(), which is called after prepare_to_rcuwait()
 	 * adds the waiter but before it has checked the wait condition.

@@ -180,9 +182,11 @@ static inline void nbcon_init(struct console *con) { }
 static inline void nbcon_free(struct console *con) { }
 static inline enum nbcon_prio nbcon_get_default_prio(void) { return NBCON_PRIO_NONE; }
 static inline void nbcon_atomic_flush_all(void) { }
-static bool nbcon_atomic_emit_next_record(struct console *con) { return false; }
+static inline bool nbcon_atomic_emit_next_record(struct console *con, bool *handover,
+						 int cookie) { return false; }
 
-static inline bool console_is_usable(struct console *con, short flags, bool use_atomic) { return false; }
+static inline bool console_is_usable(struct console *con, short flags,
+				     bool use_atomic) { return false; }
 
 #endif /* CONFIG_PRINTK */
 

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index b48b44ecbe6da..52626d0f1fa37 100644
@@ -392,8 +392,41 @@ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq,
 bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq,
 			 struct printk_info *info, unsigned int *line_count);
 
+u64 prb_first_seq(struct printk_ringbuffer *rb);
 u64 prb_first_valid_seq(struct printk_ringbuffer *rb);
 u64 prb_next_seq(struct printk_ringbuffer *rb);
 u64 prb_next_reserve_seq(struct printk_ringbuffer *rb);
 
+#ifdef CONFIG_64BIT
+
+#define __u64seq_to_ulseq(u64seq) (u64seq)
+#define __ulseq_to_u64seq(rb, ulseq) (ulseq)
+
+#else /* CONFIG_64BIT */
+
+#define __u64seq_to_ulseq(u64seq) ((u32)u64seq)
+
+static inline u64 __ulseq_to_u64seq(struct printk_ringbuffer *rb, u32 ulseq)
+{
+	u64 rb_first_seq = prb_first_seq(rb);
+	u64 seq;
+
+	/*
+	 * The provided sequence is only the lower 32 bits of the ringbuffer
+	 * sequence. It needs to be expanded to 64bit. Get the first sequence
+	 * number from the ringbuffer and fold it.
+	 *
+	 * Having a 32bit representation in the console is sufficient.
+	 * If a console ever gets more than 2^31 records behind
+	 * the ringbuffer then this is the least of the problems.
+	 *
+	 * Also the access to the ring buffer is always safe.
+	 */
+	seq = rb_first_seq - (s32)((u32)rb_first_seq - ulseq);
+
+	return seq;
+}
+
+#endif /* CONFIG_64BIT */
+
 #endif /* _KERNEL_PRINTK_RINGBUFFER_H */