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Subject[PATCH 1/3] tty: hvc: hvc_poll() fix read loop hang
Date
Patch 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.

Fixes: ec97eaad1383 ("tty: hvc: hvc_poll() break hv read loop")
Reported-by: Matteo Croce <mcroce@redhat.com>
Reported-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
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) {
--
2.18.0
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