Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753104AbcKSTAF (ORCPT ); Sat, 19 Nov 2016 14:00:05 -0500 Received: from mail-pg0-f67.google.com ([74.125.83.67]:36395 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752652AbcKSTAD (ORCPT ); Sat, 19 Nov 2016 14:00:03 -0500 Date: Sat, 19 Nov 2016 10:59:59 -0800 From: Dmitry Torokhov To: Aniroop Mathur Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] [v9]Input: evdev: fix bug of dropping valid packet after syn_dropped event Message-ID: <20161119185959.GE20446@dtor-ws> References: <1475608376-3077-1-git-send-email-a.mathur@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1475608376-3077-1-git-send-email-a.mathur@samsung.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4961 Lines: 144 Hi Anoroop, On Wed, Oct 05, 2016 at 12:42:56AM +0530, Aniroop Mathur wrote: > If last event dropped in the old queue was EV_SYN/SYN_REPORT, then lets > generate EV_SYN/SYN_REPORT immediately after queing EV_SYN/SYN_DROPPED > so that clients would not ignore next valid full packet events. > > Signed-off-by: Aniroop Mathur > > Difference from v8: > Added check for handling EVIOCG[type] ioctl for queue empty case > --- > drivers/input/evdev.c | 52 ++++++++++++++++++++++++++++++++++++++------------- > 1 file changed, 39 insertions(+), 13 deletions(-) > > diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c > index e9ae3d5..69407ff 100644 > --- a/drivers/input/evdev.c > +++ b/drivers/input/evdev.c > @@ -156,7 +156,12 @@ static void __evdev_flush_queue(struct evdev_client *client, unsigned int type) > static void __evdev_queue_syn_dropped(struct evdev_client *client) > { > struct input_event ev; > + struct input_event *last_ev; > ktime_t time; > + unsigned int mask = client->bufsize - 1; > + > + /* capture last event stored in the buffer */ > + last_ev = &client->buffer[(client->head - 1) & mask]; I am uneasy with this "looking back" into the queue. How can we be sure that we are looking at the right event? As far as I can tell we do not know if that event has been consumed or not. > > time = client->clk_type == EV_CLK_REAL ? > ktime_get_real() : > @@ -170,13 +175,28 @@ static void __evdev_queue_syn_dropped(struct evdev_client *client) > ev.value = 0; > > client->buffer[client->head++] = ev; > - client->head &= client->bufsize - 1; > + client->head &= mask; > > if (unlikely(client->head == client->tail)) { > /* drop queue but keep our SYN_DROPPED event */ > - client->tail = (client->head - 1) & (client->bufsize - 1); > + client->tail = (client->head - 1) & mask; > client->packet_head = client->tail; > } > + > + /* > + * If last packet was completely stored, then queue SYN_REPORT > + * so that clients would not ignore next valid full packet > + */ > + if (last_ev->type == EV_SYN && last_ev->code == SYN_REPORT) { > + last_ev->time = ev.time; > + client->buffer[client->head++] = *last_ev; > + client->head &= mask; > + client->packet_head = client->head; > + > + /* drop queue but keep our SYN_DROPPED & SYN_REPORT event */ > + if (unlikely(client->head == client->tail)) > + client->tail = (client->head - 2) & mask; > + } > } > > static void evdev_queue_syn_dropped(struct evdev_client *client) > @@ -218,7 +238,7 @@ static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid) > spin_lock_irqsave(&client->buffer_lock, flags); > > if (client->head != client->tail) { > - client->packet_head = client->head = client->tail; > + client->packet_head = client->tail = client->head; > __evdev_queue_syn_dropped(client); > } > > @@ -231,22 +251,24 @@ static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid) > static void __pass_event(struct evdev_client *client, > const struct input_event *event) > { > + unsigned int mask = client->bufsize - 1; > + > client->buffer[client->head++] = *event; > - client->head &= client->bufsize - 1; > + client->head &= mask; > > if (unlikely(client->head == client->tail)) { > /* > * This effectively "drops" all unconsumed events, leaving > - * EV_SYN/SYN_DROPPED plus the newest event in the queue. > + * EV_SYN/SYN_DROPPED, EV_SYN/SYN_REPORT (if required) and > + * newest event in the queue. > */ > - client->tail = (client->head - 2) & (client->bufsize - 1); > - > - client->buffer[client->tail].time = event->time; > - client->buffer[client->tail].type = EV_SYN; > - client->buffer[client->tail].code = SYN_DROPPED; > - client->buffer[client->tail].value = 0; > + client->head = (client->head - 1) & mask; > + client->packet_head = client->tail = client->head; > + __evdev_queue_syn_dropped(client); > > - client->packet_head = client->tail; > + client->buffer[client->head++] = *event; > + client->head &= mask; > + /* No need to check for buffer overflow as it just occurred */ > } > > if (event->type == EV_SYN && event->code == SYN_REPORT) { > @@ -920,6 +942,7 @@ static int evdev_handle_get_val(struct evdev_client *client, > int ret; > unsigned long *mem; > size_t len; > + bool is_queue_empty; > > len = BITS_TO_LONGS(maxbit) * sizeof(unsigned long); > mem = kmalloc(len, GFP_KERNEL); > @@ -933,12 +956,15 @@ static int evdev_handle_get_val(struct evdev_client *client, > > spin_unlock(&dev->event_lock); > > + if (client->head == client->tail) > + is_queue_empty = true; > + > __evdev_flush_queue(client, type); > > spin_unlock_irq(&client->buffer_lock); > > ret = bits_to_user(mem, maxbit, maxlen, p, compat); > - if (ret < 0) > + if (ret < 0 && !is_queue_empty) > evdev_queue_syn_dropped(client); > > kfree(mem); > -- > 2.6.2 > Thanks. -- Dmitry