[PATCH] spi: sunplus: handle signal interruption in transfer wait

[Andrew Gaylard <ag@ffroot.co.za>]

wait_for_completion_interruptible_timeout() returns -ERESTARTSYS when
interrupted by a signal, 0 on timeout, and positive on success. The
previous check was:

    if (!wait_for_completion_interruptible_timeout(...))

SIGKILL caused the interrupted path to fall through as if the transfer
succeeded. The loop then re-entered mutex_lock() on the next
iteration, which is TASK_UNINTERRUPTIBLE. The process could not be
killed while blocked there.

Check ret <= 0 and return -EINTR for the interrupted case so the process
can exit promptly on SIGKILL.

Signed-off-by: Andrew Gaylard <ag@ffroot.co.za>
---
 drivers/spi/spi-sunplus-sp7021.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-sunplus-sp7021.c b/drivers/spi/spi-sunplus-sp7021.c
index d78f48bc2b0a..607fc01c4207 100644
--- a/drivers/spi/spi-sunplus-sp7021.c
+++ b/drivers/spi/spi-sunplus-sp7021.c
@@ -338,10 +338,15 @@ static int sp7021_spi_host_transfer_one(struct spi_controller *ctlr, struct spi_
 				      SP7021_SPI_START_FD;
 		writel(reg_temp, pspim->m_base + SP7021_SPI_STATUS_REG);
 
-		if (!wait_for_completion_interruptible_timeout(&pspim->isr_done, timeout)) {
-			dev_err(&spi->dev, "wait_for_completion err\n");
-			mutex_unlock(&pspim->buf_lock);
-			return -ETIMEDOUT;
+		{
+			long ret = wait_for_completion_interruptible_timeout(
+						&pspim->isr_done, timeout);
+			if (ret <= 0) {
+				dev_err(&spi->dev, ret == 0 ? "SPI transfer timeout\n"
+							    : "SPI transfer interrupted\n");
+				mutex_unlock(&pspim->buf_lock);
+				return ret == 0 ? -ETIMEDOUT : -EINTR;
+			}
 		}
 
 		reg_temp = readl(pspim->m_base + SP7021_SPI_STATUS_REG);
-- 
2.53.0