> On 12. 04. 24, 5:38, li.ha...@zte.com.cn wrote:
> > From: Li Hao <li.ha...@zte.com.cn>
> >
> > Cancel the do_wakeup flag in hvc_struct, and change it to immediately
> > wake up tty when hp->n_outbuf is 0 in hvc_push().
> >
> > When we receive a key input character, the interrupt handling function
> > hvc_handle_interrupt() will be executed, and the echo thread
> > flush_to_ldisc() will be added to the queue.
> >
> > If the user is currently using tcsetattr(), a hang may occur. tcsetattr()
> > enters kernel and waits for hp->n_outbuf to become 0 via
> > tty_wait_until_sent(). If the echo thread finishes executing before
> > reaching tty_wait_until_sent (for example, put_chars() takes too long),
> > it will cause while meeting the wakeup condition (hp->do_wakeup = 1),
> > tty_wait_until_sent() cannot be woken up (missed the tty_wakeup() of
> > this round's tty_poll). Unless the next key input character comes,
> > hvc_poll will be executed, and tty_wakeup() will be performed through
> > the do_wakeup flag.
> >
> > Signed-off-by: Li Hao <li.ha...@zte.com.cn>
> > ---
> > drivers/tty/hvc/hvc_console.c | 12 +++++-------
> > drivers/tty/hvc/hvc_console.h | 1 -
> > 2 files changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
> > index cd1f657f7..2fa90d938 100644
> > --- a/drivers/tty/hvc/hvc_console.c
> > +++ b/drivers/tty/hvc/hvc_console.c
> > @@ -476,11 +476,13 @@ static void hvc_hangup(struct tty_struct *tty)
> > static int hvc_push(struct hvc_struct *hp)
> > {
> > int n;
> > + struct tty_struct *tty;
> >
> > n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
> > + tty = tty_port_tty_get(&hp->port);
> > if (n <= 0) {
> > if (n == 0 || n == -EAGAIN) {
> > - hp->do_wakeup = 1;
> > + tty_wakeup(tty);
>
> What if tty is NULL? Did you intent to use tty_port_tty_wakeup() instead?
>
> thanks,
> --
> js
> suse labs
Thank you for your prompt reply.
tty_port_tty_wakeup() is better, it no longer check if tty is NULL in hvc_push()
Li Hao
