Commit 6e7f6b82 authored Sep 09, 2018 by Nicholas Piggin Committed by Greg Kroah-Hartman Sep 10, 2018

tty: hvc: hvc_poll() fix read loop hang



Commit ec97eaad ("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 <mcroce@redhat.com>
Reported-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 11da3a7f

drivers/tty/hvc/hvc_console.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -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) {

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