Input: serio_raw - ensure we don't block in non-blocking read
Avoid calling wait_event_interruptible() if client requested non-blocking
read, since it is not guaranteed that another thread will not consume
event after we checked if serio_raw->head != serio_raw->tail.
Also ensure we do not return 0 but keep waiting instead in blocking case,
when another thread steals "our" byte.
Reviewed-by: David Herrmann <dh.herrmann@googlemail.com>
Reviewed-by: Che-Liang Chiou <clchiou@chromium.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/serio/serio_raw.c b/drivers/input/serio/serio_raw.c
index 948fd5a..3e24362 100644
--- a/drivers/input/serio/serio_raw.c
+++ b/drivers/input/serio/serio_raw.c
@@ -165,31 +165,38 @@
struct serio_raw *serio_raw = client->serio_raw;
char uninitialized_var(c);
ssize_t read = 0;
- int retval;
+ int error = 0;
- if (serio_raw->dead)
- return -ENODEV;
+ do {
+ if (serio_raw->dead)
+ return -ENODEV;
- if (serio_raw->head == serio_raw->tail && (file->f_flags & O_NONBLOCK))
- return -EAGAIN;
+ if (serio_raw->head == serio_raw->tail &&
+ (file->f_flags & O_NONBLOCK))
+ return -EAGAIN;
- retval = wait_event_interruptible(serio_raw->wait,
- serio_raw->head != serio_raw->tail || serio_raw->dead);
- if (retval)
- return retval;
-
- if (serio_raw->dead)
- return -ENODEV;
-
- while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {
- if (put_user(c, buffer++)) {
- retval = -EFAULT;
+ if (count == 0)
break;
- }
- read++;
- }
- return read ?: retval;
+ while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {
+ if (put_user(c, buffer++)) {
+ error = -EFAULT;
+ goto out;
+ }
+ read++;
+ }
+
+ if (read)
+ break;
+
+ if (!(file->f_flags & O_NONBLOCK))
+ error = wait_event_interruptible(serio_raw->wait,
+ serio_raw->head != serio_raw->tail ||
+ serio_raw->dead);
+ } while (!error);
+
+out:
+ return read ?: error;
}
static ssize_t serio_raw_write(struct file *file, const char __user *buffer,