um: line: Use separate IRQs per line

Today, all possible serial lines (ssl*=) as well as all
possible consoles (con*=) each share a single interrupt
(with a fixed number) with others of the same type.

Now, if you have two lines, say ssl0 and ssl1, and one
of them is connected to an fd you cannot read (e.g. a
file), but the other gets a read interrupt, then both
of them get the interrupt since it's shared. Then, the
read() call will return EOF, since it's a file being
written and there's nothing to read (at least not at
the current offset, at the end).

Unfortunately, this is treated as a read error, and we
close this line, losing all the possible output.

It might be possible to work around this and make the
IRQ sharing work, however, now that we have dynamically
allocated IRQs that are easy to use, simply use that to
achieve separating between the events; then there's no
interrupt for that line and we never attempt the read
in the first place, thus not closing the line.

This manifested itself in the wifi hostap/hwsim tests
where the parallel script communicates via one serial
console and the kernel messages go to another (a file)
and sending data on the communication console caused
the kernel messages to stop flowing into the file.

Reported-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-By: anton ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 13 insertions, 9 deletions

diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 8febf95da96e..02b0befd6763 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -139,7 +139,7 @@ static int flush_buffer(struct line *line)
 		count = line->buffer + LINE_BUFSIZE - line->head;
 
 		n = write_chan(line->chan_out, line->head, count,
-			       line->driver->write_irq);
+			       line->write_irq);
 		if (n < 0)
 			return n;
 		if (n == count) {
@@ -156,7 +156,7 @@ static int flush_buffer(struct line *line)
 
 	count = line->tail - line->head;
 	n = write_chan(line->chan_out, line->head, count,
-		       line->driver->write_irq);
+		       line->write_irq);
 
 	if (n < 0)
 		return n;
@@ -195,7 +195,7 @@ int line_write(struct tty_struct *tty, const unsigned char *buf, int len)
 		ret = buffer_data(line, buf, len);
 	else {
 		n = write_chan(line->chan_out, buf, len,
-			       line->driver->write_irq);
+			       line->write_irq);
 		if (n < 0) {
 			ret = n;
 			goto out_up;
@@ -215,7 +215,7 @@ void line_throttle(struct tty_struct *tty)
 {
 	struct line *line = tty->driver_data;
 
-	deactivate_chan(line->chan_in, line->driver->read_irq);
+	deactivate_chan(line->chan_in, line->read_irq);
 	line->throttled = 1;
 }
 
@@ -224,7 +224,7 @@ void line_unthrottle(struct tty_struct *tty)
 	struct line *line = tty->driver_data;
 
 	line->throttled = 0;
-	chan_interrupt(line, line->driver->read_irq);
+	chan_interrupt(line, line->read_irq);
 }
 
 static irqreturn_t line_write_interrupt(int irq, void *data)
@@ -260,19 +260,23 @@ int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
 	int err;
 
 	if (input) {
-		err = um_request_irq(driver->read_irq, fd, IRQ_READ,
-				     line_interrupt, IRQF_SHARED,
+		err = um_request_irq(UM_IRQ_ALLOC, fd, IRQ_READ,
+				     line_interrupt, 0,
 				     driver->read_irq_name, data);
 		if (err < 0)
 			return err;
+
+		line->read_irq = err;
 	}
 
 	if (output) {
-		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
-				     line_write_interrupt, IRQF_SHARED,
+		err = um_request_irq(UM_IRQ_ALLOC, fd, IRQ_WRITE,
+				     line_write_interrupt, 0,
 				     driver->write_irq_name, data);
 		if (err < 0)
 			return err;
+
+		line->write_irq = err;
 	}
 
 	return 0;