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[115.64.249.220]) by smtp.gmail.com with ESMTPSA id 186-v6sm6491034pgg.56.2018.09.08.22.39.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 08 Sep 2018 22:39:30 -0700 (PDT) From: Nicholas Piggin To: Greg Kroah-Hartman Cc: Nicholas Piggin , Jiri Slaby , Michael Ellerman , Matteo Croce , Jason Gunthorpe , Leon Romanovsky , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org (op) Subject: [PATCH v2 1/3] tty: hvc: hvc_poll() fix read loop hang Date: Sun, 9 Sep 2018 15:39:14 +1000 Message-Id: <20180909053916.14139-2-npiggin@gmail.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180909053916.14139-1-npiggin@gmail.com> References: <20180909053916.14139-1-npiggin@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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