4 files changed, 27 insertions, 6 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 268b62768f2b..34aacaaae14a 100644
--- a/drivers/tty/n_tty.c
+++ b/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;
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 4658e3e0ec42..06525f10e364 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/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 },
         { },
 };
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index e46e9f3f19b9..f619ad5b5eae 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/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++;
 
diff --git a/drivers/tty/tty_ldsem.c b/drivers/tty/tty_ldsem.c
index 22fad8ad5ac2..d8a55e87877f 100644
--- a/drivers/tty/tty_ldsem.c
+++ b/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;
+        }
 }
 
 /*