cpm_uart: Fix cpm uart corruption with PREEMPT_RT

Fix CPM serial port corruption when running with CONFIG_PREEMPT_RT.
Userland usage of console, and kernel printf's were stepping on each others toes.
Also only take lock if not in an oops.

Signed-off-by: Rune Torgersen <runet@innovsys.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/serial/cpm_uart/cpm_uart_core.c b/drivers/serial/cpm_uart/cpm_uart_core.c
index 43f58dc69fc9..d389a76b4afb 100644..100755
--- a/drivers/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/serial/cpm_uart/cpm_uart_core.c
@@ -969,6 +969,14 @@ static void cpm_uart_console_write(struct console *co, const char *s,
         unsigned int i;
         cbd_t __iomem *bdp, *bdbase;
         unsigned char *cp;
+        unsigned long flags;
+        int nolock = oops_in_progress;
+
+        if (unlikely(nolock)) {
+                local_irq_save(flags);
+        } else {
+                spin_lock_irqsave(&pinfo->port.lock, flags);
+        }
 
         /* Get the address of the host memory buffer.
          */
@@ -1030,6 +1038,12 @@ static void cpm_uart_console_write(struct console *co, const char *s,
                 ;
 
         pinfo->tx_cur = bdp;
+
+        if (unlikely(nolock)) {
+                local_irq_restore(flags);
+        } else {
+                spin_unlock_irqrestore(&pinfo->port.lock, flags);
+        }
 }