[PATCH] Make line/tty semantics use true write IRQ

[PATCH] Make line/tty semantics use true write IRQ

[anton.ivanov]

From: Anton Ivanov <anton.ivanov@cambridgegreys.com>

This fixes a long standing bug where large amounts of output
could freeze the tty (most commonly seen on stdio console).
While the bug has always been there it became more pronounced
after moving to the new interrupt controller.

The line semantics are now changed to have true IRQ write
semantics which should further improve the tty/line subsystem
stability and performance

Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
---
 arch/um/drivers/line.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 8d80b27502e6..7e524efed584 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -261,7 +261,7 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
 	if (err == 0) {
 		spin_unlock(&line->lock);
 		return IRQ_NONE;
-	} else if (err < 0) {
+	} else if ((err < 0) && (err != -EAGAIN)) {
 		line->head = line->buffer;
 		line->tail = line->buffer;
 	}
@@ -284,7 +284,7 @@ int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
 	if (err)
 		return err;
 	if (output)
-		err = um_request_irq(driver->write_irq, fd, IRQ_NONE,
+		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
 				     line_write_interrupt, IRQF_SHARED,
 				     driver->write_irq_name, data);
 	return err;
-- 
2.11.0


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