Merge tag 'tty-3.13-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial fixes from Greg KH:
 "Here are a few fixes for 3.13-rc5 that resolve a number of reported
  tty and serial driver issues"

* tag 'tty-3.13-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  tty: xuartps: Properly guard sysrq specific code
  n_tty: Fix apparent order of echoed output
  serial: 8250_dw: add new ACPI IDs
  serial: 8250_dw: Fix LCR workaround regression
  tty: Fix hang at ldsem_down_read()

drivers/tty/n_tty.c

@@ -93,6 +93,7 @@ struct n_tty_data {
 	size_t canon_head;
 	size_t echo_head;
 	size_t echo_commit;
+	size_t echo_mark;
 	DECLARE_BITMAP(char_map, 256);
 
 	/* private to n_tty_receive_overrun (single-threaded) */
@@ -336,6 +337,7 @@ static void reset_buffer_flags(struct n_tty_data *ldata)
 {
 	ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
 	ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
+	ldata->echo_mark = 0;
 	ldata->line_start = 0;
 
 	ldata->erasing = 0;
@@ -787,6 +789,7 @@ static void commit_echoes(struct tty_struct *tty)
 	size_t head;
 
 	head = ldata->echo_head;
+	ldata->echo_mark = head;
 	old = ldata->echo_commit - ldata->echo_tail;
 
 	/* Process committed echoes if the accumulated # of bytes
@@ -811,10 +814,11 @@ static void process_echoes(struct tty_struct *tty)
 	size_t echoed;
 
 	if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
-	    ldata->echo_commit == ldata->echo_tail)
+	    ldata->echo_mark == ldata->echo_tail)
 		return;
 
 	mutex_lock(&ldata->output_lock);
+	ldata->echo_commit = ldata->echo_mark;
 	echoed = __process_echoes(tty);
 	mutex_unlock(&ldata->output_lock);
 
@@ -822,6 +826,7 @@ static void process_echoes(struct tty_struct *tty)
 		tty->ops->flush_chars(tty);
 }
 
+/* NB: echo_mark and echo_head should be equivalent here */
 static void flush_echoes(struct tty_struct *tty)
 {
 	struct n_tty_data *ldata = tty->disc_data;

drivers/tty/serial/8250/8250_dw.c

@@ -96,7 +96,8 @@ static void dw8250_serial_out(struct uart_port *p, int offset, int value)
 	if (offset == UART_LCR) {
 		int tries = 1000;
 		while (tries--) {
-			if (value == p->serial_in(p, UART_LCR))
+			unsigned int lcr = p->serial_in(p, UART_LCR);
+			if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
 				return;
 			dw8250_force_idle(p);
 			writeb(value, p->membase + (UART_LCR << p->regshift));
@@ -132,7 +133,8 @@ static void dw8250_serial_out32(struct uart_port *p, int offset, int value)
 	if (offset == UART_LCR) {
 		int tries = 1000;
 		while (tries--) {
-			if (value == p->serial_in(p, UART_LCR))
+			unsigned int lcr = p->serial_in(p, UART_LCR);
+			if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
 				return;
 			dw8250_force_idle(p);
 			writel(value, p->membase + (UART_LCR << p->regshift));
@@ -455,6 +457,8 @@ MODULE_DEVICE_TABLE(of, dw8250_of_match);
 static const struct acpi_device_id dw8250_acpi_match[] = {
 	{ "INT33C4", 0 },
 	{ "INT33C5", 0 },
+	{ "INT3434", 0 },
+	{ "INT3435", 0 },
 	{ "80860F0A", 0 },
 	{ },
 };

drivers/tty/serial/xilinx_uartps.c

@@ -240,6 +240,7 @@ static irqreturn_t xuartps_isr(int irq, void *dev_id)
 					continue;
 			}
 
+#ifdef SUPPORT_SYSRQ
 			/*
 			 * uart_handle_sysrq_char() doesn't work if
 			 * spinlocked, for some reason
@@ -253,6 +254,7 @@ static irqreturn_t xuartps_isr(int irq, void *dev_id)
 				}
 				spin_lock(&port->lock);
 			}
+#endif
 
 			port->icount.rx++;
 

drivers/tty/tty_ldsem.c

@@ -86,11 +86,21 @@ static inline long ldsem_atomic_update(long delta, struct ld_semaphore *sem)
 	return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
 }
 
+/*
+ * ldsem_cmpxchg() updates @*old with the last-known sem->count value.
+ * Returns 1 if count was successfully changed; @*old will have @new value.
+ * Returns 0 if count was not changed; @*old will have most recent sem->count
+ */
 static inline int ldsem_cmpxchg(long *old, long new, struct ld_semaphore *sem)
 {
-	long tmp = *old;
-	*old = atomic_long_cmpxchg(&sem->count, *old, new);
-	return *old == tmp;
+	long tmp = atomic_long_cmpxchg(&sem->count, *old, new);
+	if (tmp == *old) {
+		*old = new;
+		return 1;
+	} else {
+		*old = tmp;
+		return 0;
+	}
 }
 
 /*