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Input: serio_raw - ensure we don't block in non-blocking read

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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>
This commit is contained in:
Dmitry Torokhov
2012-04-20 22:33:08 -07:00
parent 71f3d070a3
commit 486c8aba39
1 changed files with 27 additions and 20 deletions
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47
drivers/input/serio/serio_raw.c
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@@ -165,31 +165,38 @@ static ssize_t serio_raw_read(struct file *file, char __user *buffer,
struct serio_raw *serio_raw = client->serio_raw; struct serio_raw *serio_raw = client->serio_raw;
char uninitialized_var(c); char uninitialized_var(c);
ssize_t read = 0; ssize_t read = 0;
int retval; int error = 0;
if (serio_raw->dead) do {
return -ENODEV; if (serio_raw->dead)
return -ENODEV;
if (serio_raw->head == serio_raw->tail && (file->f_flags & O_NONBLOCK)) if (serio_raw->head == serio_raw->tail &&
return -EAGAIN; (file->f_flags & O_NONBLOCK))
return -EAGAIN;
retval = wait_event_interruptible(serio_raw->wait, if (count == 0)
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;
break; 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, static ssize_t serio_raw_write(struct file *file, const char __user *buffer,