[PATCH v3 05/12] OMAP: Serial: Hold console lock for console usage.

[Govindraj.R]

Acquire console lock before enabling and writing to console-uart
to avoid any recursive prints from console write.
for ex:
        --> printk
          --> uart_console_write
            --> get_sync
              --> printk from omap_device enable
                --> uart_console write

Use RPM_SUSPENDING check to avoid below scenario during bootup
As during bootup console_lock is not available.
       --> uart_add_one_port
           --> console_register
               --> console_lock
                --> console_unlock
                     --> call_console_drivers (here yet console_lock is not released)
                          --> uart_console_write

Acked-by: Alan Cox <alan at linux.intel.com>
Signed-off-by: Govindraj.R <govindraj.raja at ti.com>
---
 drivers/tty/serial/omap-serial.c |   20 +++++++++++++++++++-
 1 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 897416f..ee94291 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1008,7 +1008,22 @@ serial_omap_console_write(struct console *co, const char *s,
 	struct uart_omap_port *up = serial_omap_console_ports[co->index];
 	unsigned long flags;
 	unsigned int ier;
-	int locked = 1;
+	int console_lock = 0, locked = 1;
+
+	if (console_trylock())
+		console_lock = 1;
+
+	/*
+	 * If console_lock is not available and we are in suspending
+	 * state then we can avoid the console usage scenario
+	 * as this may introduce recursive prints.
+	 * Basically this scenario occurs during boot while
+	 * printing debug bootlogs.
+	 */
+
+	if (!console_lock &&
+		up->pdev->dev.power.runtime_status == RPM_SUSPENDING)
+		return;
 
 	local_irq_save(flags);
 	if (up->port.sysrq)
@@ -1044,6 +1059,9 @@ serial_omap_console_write(struct console *co, const char *s,
 	if (up->msr_saved_flags)
 		check_modem_status(up);
 
+	if (console_lock)
+		console_unlock();
+
 	serial_omap_port_disable(up);
 	if (locked)
 		spin_unlock(&up->port.lock);
-- 
1.7.0.4