Re: lockdep input layer warnings.

[Arjan van de Ven]

On Thu, 2006-07-06 at 16:29 -0400, Dmitry Torokhov wrote:
> On 7/6/06, Arjan van de Ven <arjan@xxxxxxxxxxxxx> wrote:
> > On Thu, 2006-07-06 at 14:37 -0400, Dmitry Torokhov wrote:
> > > On 7/6/06, Dave Jones <davej@xxxxxxxxxx> wrote:
> > > > One of our Fedora-devel users picked up on this this morning
> > > > in an 18rc1 based kernel.
> > > >
> > > >                Dave
> > > >
> > > >
> > > >  Synaptics Touchpad, model: 1, fw: 5.9, id: 0x2c6ab1, caps: 0x884793/0x0
> > > >  serio: Synaptics pass-through port at isa0060/serio1/input0
> > > >  input: SynPS/2 Synaptics TouchPad as /class/input/input1
> > > >  PM: Adding info for serio:serio2
> > > >
> > > >  =============================================
> > > >  [ INFO: possible recursive locking detected ]
> > > >  ---------------------------------------------
> > >
> > > False alarm, there was a lockdep annotating patch for it in -mm.
> > not so sure; that patch is supposed to be in -rc1 already; investigating
> >
> 
> Well, you are right, the patch is in -rc1 and I see mutex_lock_nested
> in the backtrace but for some reason it is still not happy. Again,
> this is with pass-through Synaptics port and we first taking mutex of
> the child device and then (going through pass-through port) trying to
> take mutex of the parent.

Ok it seems more drastic measures are needed; and a split of the
cmd_mutex class on a per driver basis. The easiest way to do that is to
inline the lock initialization (patch below) but to be honest I think
the patch is a bit ugly; I considered inlining the entire function
instead, any opinions on that?

Index: linux-2.6.18-rc1/drivers/input/serio/libps2.c
===================================================================
--- linux-2.6.18-rc1.orig/drivers/input/serio/libps2.c
+++ linux-2.6.18-rc1/drivers/input/serio/libps2.c
@@ -27,7 +27,7 @@ MODULE_AUTHOR("Dmitry Torokhov <dtor@mai
 MODULE_DESCRIPTION("PS/2 driver library");
 MODULE_LICENSE("GPL");
 
-EXPORT_SYMBOL(ps2_init);
+EXPORT_SYMBOL(__ps2_init);
 EXPORT_SYMBOL(ps2_sendbyte);
 EXPORT_SYMBOL(ps2_drain);
 EXPORT_SYMBOL(ps2_command);
@@ -177,7 +177,7 @@ int ps2_command(struct ps2dev *ps2dev, u
 		return -1;
 	}
 
-	mutex_lock_nested(&ps2dev->cmd_mutex, SINGLE_DEPTH_NESTING);
+	mutex_lock(&ps2dev->cmd_mutex);
 
 	serio_pause_rx(ps2dev->serio);
 	ps2dev->flags = command == PS2_CMD_GETID ? PS2_FLAG_WAITID : 0;
@@ -279,7 +279,7 @@ int ps2_schedule_command(struct ps2dev *
  * ps2_init() initializes ps2dev structure
  */
 
-void ps2_init(struct ps2dev *ps2dev, struct serio *serio)
+void __ps2_init(struct ps2dev *ps2dev, struct serio *serio)
 {
 	mutex_init(&ps2dev->cmd_mutex);
 	init_waitqueue_head(&ps2dev->wait);
Index: linux-2.6.18-rc1/include/linux/libps2.h
===================================================================
--- linux-2.6.18-rc1.orig/include/linux/libps2.h
+++ linux-2.6.18-rc1/include/linux/libps2.h
@@ -39,7 +39,12 @@ struct ps2dev {
 	unsigned char nak;
 };
 
-void ps2_init(struct ps2dev *ps2dev, struct serio *serio);
+void __ps2_init(struct ps2dev *ps2dev, struct serio *serio);
+static inline void ps2_init(struct ps2dev *ps2dev, struct serio *serio)
+{
+	__ps2_init(ps2dev, serio);
+	mutex_init(&ps2dev->cmd_mutex);
+}
 int ps2_sendbyte(struct ps2dev *ps2dev, unsigned char byte, int timeout);
 void ps2_drain(struct ps2dev *ps2dev, int maxbytes, int timeout);
 int ps2_command(struct ps2dev *ps2dev, unsigned char *param, int command);


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