On Tue, 28 Aug 2018 12:54:08 +0000
Matteo Croce <mcr...@redhat.com> wrote:
> With kernel 4.19.0-rc1 virtio_console hangs very often.
> I can always trigger the bug by pasting some characters in the
> terminal window, the console will stop receiving keypresses, but I can
> still see output from the console.
> Stangely, logging in the VM via SSH and sending lot of data to hvc0,
> like 'dmesg >/dev/hvc0' will fix the issue until the next paste.
>
> I did a git bisect and I've found that this is the offending commit,
> reverting it fixes it.
>
> Cheers,
>
> commit ec97eaad1383ab2500fcf9a07ade6044fbcc67f5
> Author: Nicholas Piggin <npig...@gmail.com>
> Date: Tue May 1 00:55:54 2018 +1000
>
> tty: hvc: hvc_poll() break hv read loop
Thanks for the report. I can't immediately see what the problem
is. Can you try get a stack trace of where it is stuck?
Perhaps try this patch if you have time (it's a bit of a shot
in the dark).
Thanks,
Nick
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 5414c4a87bea..ac45235832f1 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -635,6 +635,7 @@ static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
int read_total = 0;
int written_total = 0;
+again:
spin_lock_irqsave(&hp->lock, flags);
/* Push pending writes */
@@ -721,6 +722,10 @@ static int __hvc_poll(struct hvc_struct *hp, bool
may_sleep)
poll_mask |= HVC_POLL_READ;
read_total = n;
+ spin_unlock_irqrestore(&hp->lock, flags);
+ cond_resched();
+ goto again;
+
out:
/* Wakeup write queue if necessary */
if (hp->do_wakeup) {
