The patch titled
atmel_serial: fix hang in set_termios when crtscts is enabled
has been added to the -mm tree. Its filename is
atmel_serial-fix-hang-in-set_termios-when-crtscts-is-enabled.patch
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------------------------------------------------------
Subject: atmel_serial: fix hang in set_termios when crtscts is enabled
From: Haavard Skinnemoen <haavard.skinnemoen@xxxxxxxxx>
After enabling hardware flow control, any subsequent termios call may hang
waiting for the transmitter to drain. This appears to be caused by a
busy-loop in set_termios() waiting for the transmitter to become empty,
which may take a very long time (or hang indefinitely) if the device at
the other end is blocking us.
A quick look through the tty and serial_core code indicates that any
necessary flushing (which is optional) has already been done at this
point, so there's no need for the driver to flush the transmitter on its
own.
Fix it by removing the busy-loop altogether.
Tested-by: Eirik Aanonsen <eaa@xxxxxxxxxxxxxx>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@xxxxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/serial/atmel_serial.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff -puN drivers/serial/atmel_serial.c~atmel_serial-fix-hang-in-set_termios-when-crtscts-is-enabled drivers/serial/atmel_serial.c
--- a/drivers/serial/atmel_serial.c~atmel_serial-fix-hang-in-set_termios-when-crtscts-is-enabled
+++ a/drivers/serial/atmel_serial.c
@@ -1104,11 +1104,13 @@ static void atmel_set_termios(struct uar
/* update the per-port timeout */
uart_update_timeout(port, termios->c_cflag, baud);
- /* save/disable interrupts and drain transmitter */
+ /*
+ * save/disable interrupts. The tty layer will ensure that the
+ * transmitter is empty if requested by the caller, so there's
+ * no need to wait for it here.
+ */
imr = UART_GET_IMR(port);
UART_PUT_IDR(port, -1);
- while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
- cpu_relax();
/* disable receiver and transmitter */
UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS);
_
Patches currently in -mm which might be from haavard.skinnemoen@xxxxxxxxx are
linux-next.patch
atmel_serial-fix-hang-in-set_termios-when-crtscts-is-enabled.patch
atmel-lcdc-fix-pixclock-upper-bound-detection.patch
ptrace-remove-pt_dtrace-from-avr32-mn10300-parisc-s390-sh-xtensa.patch
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