Commit e725a494 authored Jun 23, 2010 by Henrik Rydberg Committed by Dmitry Torokhov Jun 23, 2010

Input: evdev - never leave the client buffer empty after write



When the client buffer is very small and wraps around a lot, it may
well be that a write increases the head such that head == tail. If
this happens between the point where a poll is triggered and the
actual data is being read, there will be no data to read. This is
confusing to applications, which might end up closing the file.

This patch solves the problem by making sure the client buffer is
never empty after writing to it.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

parent 6967b4d9

drivers/input/evdev.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -54,11 +54,15 @@ static void evdev_pass_event(struct evdev_client *client,
		struct input_event *event)
		{
		/*
		* Interrupts are disabled, just acquire the lock
		* Interrupts are disabled, just acquire the lock.
		* Make sure we don't leave with the client buffer
		* "empty" by having client->head == client->tail.
		*/
		spin_lock(&client->buffer_lock);
		do {
		client->buffer[client->head++] = *event;
		client->head &= client->bufsize - 1;
		} while (client->head == client->tail);
		spin_unlock(&client->buffer_lock);

		if (event->type == EV_SYN)

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