From 6e7f6b82c60afb46ff71c2127421c66207966d6d Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Sun, 9 Sep 2018 15:39:14 +1000 Subject: [PATCH] tty: hvc: hvc_poll() fix read loop hang Commit ec97eaad1383 ("tty: hvc: hvc_poll() break hv read loop") causes the virtio console to hang at times (e.g., if you paste a bunch of characters to it. The reason is that get_chars must return 0 before we can be sure the driver will kick or poll input again, but this change only scheduled a poll if get_chars had returned a full count. Change this to poll on any > 0 count. Reported-by: Matteo Croce Reported-by: Jason Gunthorpe Tested-by: Matteo Croce Tested-by: Jason Gunthorpe Tested-by: Leon Romanovsky Signed-off-by: Nicholas Piggin Signed-off-by: Greg Kroah-Hartman --- drivers/tty/hvc/hvc_console.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c index 5414c4a87bea..c917749708d2 100644 --- a/drivers/tty/hvc/hvc_console.c +++ b/drivers/tty/hvc/hvc_console.c @@ -717,10 +717,13 @@ static int __hvc_poll(struct hvc_struct *hp, bool may_sleep) #endif /* CONFIG_MAGIC_SYSRQ */ tty_insert_flip_char(&hp->port, buf[i], 0); } - if (n == count) - poll_mask |= HVC_POLL_READ; read_total = n; + /* + * Latency break, schedule another poll immediately. + */ + poll_mask |= HVC_POLL_READ; + out: /* Wakeup write queue if necessary */ if (hp->do_wakeup) { -- 2.30.2