From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: linux-input@vger.kernel.org
Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>,
Che-Liang Chiou <clchiou@chromium.org>,
David Herrmann <dh.herrmann@googlemail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Input: serio_raw - ensure we don't block in non-blocking read
Date: Wed, 11 Apr 2012 00:23:00 -0700 [thread overview]
Message-ID: <20120411072300.GA15759@core.coreip.homeip.net> (raw)
In-Reply-To: <20120403202432.GA18564@core.coreip.homeip.net>
On Tue, Apr 03, 2012 at 01:24:33PM -0700, Dmitry Torokhov wrote:
> Avoid calling wait_event_interruptible() if client requested non-blocking
> read, since it is not guaranteed that another thread will not consume
> event after we checked if serio_raw->head != serio_raw->tail.
>
> Also ensure we do not return 0 but keep waiting instead in blocking case,
> when another thread steals "our" byte.
>
> Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Anyone? It would be nice if someone could review my patches as well,
otherwise we may end up with breakages...
Thanks.
> ---
> drivers/input/serio/serio_raw.c | 43 ++++++++++++++++++++++----------------
> 1 files changed, 25 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/input/serio/serio_raw.c b/drivers/input/serio/serio_raw.c
> index 4494233..094d6fb 100644
> --- a/drivers/input/serio/serio_raw.c
> +++ b/drivers/input/serio/serio_raw.c
> @@ -165,31 +165,38 @@ static ssize_t serio_raw_read(struct file *file, char __user *buffer,
> struct serio_raw *serio_raw = client->serio_raw;
> char uninitialized_var(c);
> ssize_t read = 0;
> - int retval;
> + int error = 0;
>
> - if (serio_raw->dead)
> - return -ENODEV;
> + do {
> + if (serio_raw->dead)
> + return -ENODEV;
>
> - if (serio_raw->head == serio_raw->tail && (file->f_flags & O_NONBLOCK))
> - return -EAGAIN;
> + if (serio_raw->head == serio_raw->tail &&
> + (file->f_flags & O_NONBLOCK))
> + return -EAGAIN;
>
> - retval = wait_event_interruptible(serio_raw->wait,
> - serio_raw->head != serio_raw->tail || serio_raw->dead);
> - if (retval)
> - return retval;
> + if (count == 0)
> + break;
>
> - if (serio_raw->dead)
> - return -ENODEV;
> + while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {
> + if (put_user(c, buffer++)) {
> + error = -EFAULT;
> + goto out;
> + }
> + read++;
> + }
>
> - while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {
> - if (put_user(c, buffer++)) {
> - retval = -EFAULT;
> + if (read)
> break;
> - }
> - read++;
> - }
>
> - return read ?: retval;
> + if (!(file->f_flags & O_NONBLOCK))
> + error = wait_event_interruptible(serio_raw->wait,
> + serio_raw->head != serio_raw->tail ||
> + serio_raw->dead);
> + } while (!error);
> +
> +out:
> + return read ?: error;
> }
>
> static ssize_t serio_raw_write(struct file *file, const char __user *buffer,
> --
> 1.7.7.6
>
--
Dmitry
next prev parent reply other threads:[~2012-04-11 7:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-03 20:24 [PATCH] Input: serio_raw - ensure we don't block in non-blocking read Dmitry Torokhov
2012-04-11 7:23 ` Dmitry Torokhov [this message]
2012-04-13 16:50 ` David Herrmann
2012-04-17 8:56 ` Che-liang Chiou
2012-04-17 9:14 ` Che-liang Chiou
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