Trasmitted characters could be lost or written twice due to a missing lock
in the critical section of the isr. The missing lock causes a race condition
on SMP systems between ulite_transmit when called from the isr and
ulite_start_tx as they can execute simultaneously on separate cores. The call
from ulite_start_tx is made from serial_core.c with the lock taken.
Signed-off-by: Kris Modrak <krismodrak@xxxxxxxxxxx>
---
drivers/tty/serial/uartlite.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/drivers/tty/serial/uartlite.c b/drivers/tty/serial/uartlite.c
index 9fc22f4..ee151a2 100644
--- a/drivers/tty/serial/uartlite.c
+++ b/drivers/tty/serial/uartlite.c
@@ -196,9 +196,13 @@ static irqreturn_t ulite_isr(int irq, void *dev_id)
int busy, n = 0;
do {
- int stat = uart_in32(ULITE_STATUS, port);
+ int stat;
+
+ spin_lock(&port->lock);
+ stat = uart_in32(ULITE_STATUS, port);
busy = ulite_receive(port, stat);
busy |= ulite_transmit(port, stat);
+ spin_unlock(&port->lock);
n++;
} while (busy);
--
1.7.5.4
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