From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Raul E Rangel <rrangel@chromium.org>
Cc: linux-input <linux-input@vger.kernel.org>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
"S, Shirish" <Shirish.S@amd.com>,
Andy Shevchenko <andy@infradead.org>, Dan Murphy <dmurphy@ti.com>,
Darren Hart <dvhart@infradead.org>,
Jacek Anaszewski <jacek.anaszewski@gmail.com>,
"Lee, Chun-Yi" <jlee@suse.com>, Pavel Machek <pavel@ucw.cz>,
Rajat Jain <rajatja@google.com>,
Stephen Boyd <swboyd@chromium.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux LED Subsystem <linux-leds@vger.kernel.org>,
Platform Driver <platform-driver-x86@vger.kernel.org>
Subject: Re: [PATCH 1/2] Input: i8042 - Prevent intermixing i8042 commands
Date: Thu, 27 Aug 2020 23:12:33 +0300 [thread overview]
Message-ID: <CAHp75VfM-61vN_Ptz1YWz3JmRJ7eqssVykXuCircuiz9HL3TVA@mail.gmail.com> (raw)
In-Reply-To: <20200827135205.1.I6981f9a9f0c12e60f8038f3b574184f8ffc1b9b5@changeid>
On Thu, Aug 27, 2020 at 10:52 PM Raul E Rangel <rrangel@chromium.org> wrote:
>
> The i8042_mutex must be held by writers of the AUX and KBD ports, as
> well as users of i8042_command. There were a lot of users of
> i8042_command that were not calling i8042_lock_chip/i8042_unlock_chip.
> This resulted in i8042_commands being issues in between PS/2
> transactions.
>
> This change moves the mutex lock into i8042_command and removes the
> burden of locking the mutex from the callers.
Which is wrong according to your very patch. See below.
> It is expected that the i8042_mutex is locked before calling
> i8042_aux_write or i8042_kbd_write. This is currently done by the PS/2
> layer via ps2_begin_command and ps2_end_command. Other modules
> (serio_raw) do not currently lock the mutex, so there is still a
> possibility for intermixed commands.
...
> + mutex_lock(&i8042_mutex);
> +
> spin_lock_irqsave(&i8042_lock, flags);
> retval = __i8042_command(param, command);
> spin_unlock_irqrestore(&i8042_lock, flags);
>
> + mutex_unlock(&i8042_mutex);
Question 1. Why do you need mutex at all in the above situation? Spin
lock isn't enough?
...
> - i8042_lock_chip();
> -
> if (value == LED_OFF)
> i8042_command(NULL, CLEVO_MAIL_LED_OFF);
> else if (value <= LED_HALF)
> i8042_command(NULL, CLEVO_MAIL_LED_BLINK_0_5HZ);
> else
> i8042_command(NULL, CLEVO_MAIL_LED_BLINK_1HZ);
> -
> - i8042_unlock_chip();
> -
Now, these three commands are not considered as a transaction (no
atomicity). That's why your patch is wrong.
> }
...
> int rc;
>
> - i8042_lock_chip();
> rc = i8042_command(¶m, A1655_WIFI_COMMAND);
> - i8042_unlock_chip();
> return rc;
rc become redundant.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2020-08-27 20:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-27 19:52 [PATCH 1/2] Input: i8042 - Prevent intermixing i8042 commands Raul E Rangel
2020-08-27 19:52 ` [PATCH 2/2] Input: i8042 - Lock i8042_mutex before flushing Raul E Rangel
2020-08-27 20:12 ` Andy Shevchenko [this message]
2020-08-27 20:18 ` [PATCH 1/2] Input: i8042 - Prevent intermixing i8042 commands Andy Shevchenko
2020-08-27 20:20 ` Raul Rangel
2020-08-29 7:47 ` Pavel Machek
2020-08-31 13:39 ` Raul Rangel
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