linux-kernel - Sysctl locking?

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Date:	Mon, 4 Oct 2010 22:03:35 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Linux Input <linux-input@...r.kernel.org>
Subject: Sysctl locking?

Hi,

I tried tracing through sysctl code and it appears that there is no
generic locking for reads and writes to a sysctl node and thus a patch
like below is needed if proc_handler is a bit more complex than simply
storing an integer value.

Am I missing something?

Thanks.

--  
Dmitry

Input: mac mouse emulation - add locking

We need to add appropriate locking when toggling mac mouse emulation
on and off to ensure that input device and handler are in consistent
state.

Signed-off-by: Dmitry Torokhov <dtor@...l.ru>
---

 drivers/macintosh/mac_hid.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/drivers/macintosh/mac_hid.c b/drivers/macintosh/mac_hid.c
index 067f996..6a82388 100644
--- a/drivers/macintosh/mac_hid.c
+++ b/drivers/macintosh/mac_hid.c
@@ -23,6 +23,8 @@ static int mouse_button3_keycode = KEY_RIGHTALT;	/* right option key */

 static struct input_dev *mac_hid_emumouse_dev;

+static DEFINE_MUTEX(mac_hid_emumouse_mutex);
+
 static int mac_hid_create_emumouse(void)
 {
 	static struct lock_class_key mac_hid_emumouse_dev_event_class;
@@ -187,6 +189,10 @@ static int mac_hid_toggle_emumouse(ctl_table *table, int write,
 	int old_val = *valp;
 	int rc;

+	rc = mutex_lock_killable(&mac_hid_emumouse_mutex);
+	if (rc)
+		return rc;
+
 	rc = proc_dointvec(table, write, buffer, lenp, ppos);

 	if (rc == 0 && write && *valp != old_val) {
@@ -202,6 +208,8 @@ static int mac_hid_toggle_emumouse(ctl_table *table, int write,
 	if (rc)
 		*valp = old_val;

+	mutex_unlock(&mac_hid_emumouse_mutex);
+
 	return rc;
 }

--
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