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.
Signed-off-by: Dmitry Torokhov <dtor@xxxxxxx>
---
drivers/input/serio/serio_raw.c | 43 ++++++++++++++++++++++----------------
1 files changed, 25 insertions(+), 18 deletions(-)
diff --git a/drivers/input/serio/serio_raw.c b/drivers/input/serio/serio_raw.c
index 4494233..094d6fb 100644
--- a/drivers/input/serio/serio_raw.c
+++ b/drivers/input/serio/serio_raw.c
@@ -165,31 +165,38 @@ static ssize_t serio_raw_read(struct file *file, char __user *buffer,
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 (count == 0)
+ break;
- if (serio_raw->dead)
- return -ENODEV;
+ while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {
+ if (put_user(c, buffer++)) {
+ error = -EFAULT;
+ goto out;
+ }
+ read++;
+ }
- while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {
- if (put_user(c, buffer++)) {
- retval = -EFAULT;
+ if (read)
break;
- }
- read++;
- }
- return read ?: retval;
+ 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,
--
1.7.7.6
--
Dmitry
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
