[2.6 RFC/PATCH] Input: possible deadlock in i8042

[2.6 RFC/PATCH] Input: possible deadlock in i8042

[Dmitry Torokhov]

If request_irq fails in i8042_open it will call serio_unregister_port,
which takes serio_sem. i8042_open may be called:

serio_register_port - serio_find_dev - dev->connect
serio_register_device - dev->connect

Both serio_register_port and serio_register_device take serio_sem as well.

I think that serio_{register|unregister}_port can be converted into
submitting requests to kseriod thus removing deadlock on the serio_sem.

The patch below is on top of serio* patches in Andrew Morton's -mm tree.

Dmitry

===================================================================


ChangeSet@1.1512, 2003-11-30 02:42:54-05:00, dtor_core@ameritech.net
  Input: Use kseriod to register/unregister serio ports


 serio.c |   22 ++++++++++++++--------
 1 files changed, 14 insertions(+), 8 deletions(-)

===================================================================

diff -Nru a/drivers/input/serio/serio.c b/drivers/input/serio/serio.c
--- a/drivers/input/serio/serio.c	Sun Nov 30 03:01:40 2003
+++ b/drivers/input/serio/serio.c	Sun Nov 30 03:01:40 2003
@@ -83,8 +83,10 @@
 	}
 }
 
-#define SERIO_RESCAN	1
-#define SERIO_RECONNECT	2
+#define SERIO_RESCAN		1
+#define SERIO_RECONNECT		2
+#define SERIO_REGISTER_PORT	3
+#define SERIO_UNREGISTER_PORT	4
 
 static DECLARE_WAIT_QUEUE_HEAD(serio_wait);
 static DECLARE_COMPLETION(serio_exited);
@@ -111,6 +113,14 @@
 			goto event_done;
 		
 		switch (event->type) {
+			case SERIO_REGISTER_PORT :
+				__serio_register_port(event->serio);
+				break;
+
+			case SERIO_UNREGISTER_PORT :
+				__serio_unregister_port(event->serio);
+				break;
+
 			case SERIO_RECONNECT :
 				if (event->serio->dev && event->serio->dev->reconnect)
 					if (event->serio->dev->reconnect(event->serio) == 0)
@@ -192,9 +202,7 @@
 
 void serio_register_port(struct serio *serio)
 {
-	down(&serio_sem);
-	__serio_register_port(serio);
-	up(&serio_sem);
+	serio_queue_event(serio, SERIO_REGISTER_PORT);
 }
 
 /*
@@ -210,9 +218,7 @@
 
 void serio_unregister_port(struct serio *serio)
 {
-	down(&serio_sem);
-	__serio_unregister_port(serio);
-	up(&serio_sem);
+	serio_queue_event(serio, SERIO_UNREGISTER_PORT);
 }
 
 /*

Re: [2.6 RFC/PATCH] Input: possible deadlock in i8042

[Vojtech Pavlik]

On Sun, Nov 30, 2003 at 03:03:57AM -0500, Dmitry Torokhov wrote:
> If request_irq fails in i8042_open it will call serio_unregister_port,
> which takes serio_sem. i8042_open may be called:
> 
> serio_register_port - serio_find_dev - dev->connect
> serio_register_device - dev->connect
> 
> Both serio_register_port and serio_register_device take serio_sem as well.
> 
> I think that serio_{register|unregister}_port can be converted into
> submitting requests to kseriod thus removing deadlock on the serio_sem.
> 
> The patch below is on top of serio* patches in Andrew Morton's -mm tree.

It's nice to avoid the deadlock this way, but I think it's not a good
idea to make the register/unregister asynchronous - it could be a nasty
surprise for an unsuspecting driver writer.

> Dmitry
> 
> ===================================================================
> 
> 
> ChangeSet@1.1512, 2003-11-30 02:42:54-05:00, dtor_core@ameritech.net
>   Input: Use kseriod to register/unregister serio ports
> 
> 
>  serio.c |   22 ++++++++++++++--------
>  1 files changed, 14 insertions(+), 8 deletions(-)
> 
> ===================================================================
> 
> diff -Nru a/drivers/input/serio/serio.c b/drivers/input/serio/serio.c
> --- a/drivers/input/serio/serio.c	Sun Nov 30 03:01:40 2003
> +++ b/drivers/input/serio/serio.c	Sun Nov 30 03:01:40 2003
> @@ -83,8 +83,10 @@
>  	}
>  }
>  
> -#define SERIO_RESCAN	1
> -#define SERIO_RECONNECT	2
> +#define SERIO_RESCAN		1
> +#define SERIO_RECONNECT		2
> +#define SERIO_REGISTER_PORT	3
> +#define SERIO_UNREGISTER_PORT	4
>  
>  static DECLARE_WAIT_QUEUE_HEAD(serio_wait);
>  static DECLARE_COMPLETION(serio_exited);
> @@ -111,6 +113,14 @@
>  			goto event_done;
>  		
>  		switch (event->type) {
> +			case SERIO_REGISTER_PORT :
> +				__serio_register_port(event->serio);
> +				break;
> +
> +			case SERIO_UNREGISTER_PORT :
> +				__serio_unregister_port(event->serio);
> +				break;
> +
>  			case SERIO_RECONNECT :
>  				if (event->serio->dev && event->serio->dev->reconnect)
>  					if (event->serio->dev->reconnect(event->serio) == 0)
> @@ -192,9 +202,7 @@
>  
>  void serio_register_port(struct serio *serio)
>  {
> -	down(&serio_sem);
> -	__serio_register_port(serio);
> -	up(&serio_sem);
> +	serio_queue_event(serio, SERIO_REGISTER_PORT);
>  }
>  
>  /*
> @@ -210,9 +218,7 @@
>  
>  void serio_unregister_port(struct serio *serio)
>  {
> -	down(&serio_sem);
> -	__serio_unregister_port(serio);
> -	up(&serio_sem);
> +	serio_queue_event(serio, SERIO_UNREGISTER_PORT);
>  }
>  
>  /*
> 

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR

Re: [2.6 RFC/PATCH] Input: possible deadlock in i8042

[Dmitry Torokhov]

On Sunday 30 November 2003 04:00 am, Vojtech Pavlik wrote:
> On Sun, Nov 30, 2003 at 03:03:57AM -0500, Dmitry Torokhov wrote:
> > If request_irq fails in i8042_open it will call
> > serio_unregister_port, which takes serio_sem. i8042_open may be
> > called:
> >
> > serio_register_port - serio_find_dev - dev->connect
> > serio_register_device - dev->connect
> >
> > Both serio_register_port and serio_register_device take serio_sem as
> > well.
> >
> > I think that serio_{register|unregister}_port can be converted into
> > submitting requests to kseriod thus removing deadlock on the
> > serio_sem.
> >
> > The patch below is on top of serio* patches in Andrew Morton's -mm
> > tree.
>
> It's nice to avoid the deadlock this way, but I think it's not a good
> idea to make the register/unregister asynchronous - it could be a nasty
> surprise for an unsuspecting driver writer.
>

Serio_register_port is not guaranteed to find a driver for the serio anyway
as the driver can be compiled as a module and loaded much much later so it
should not be a concern. It is somewhat asynchronous already.

Dmitry

Re: [2.6 RFC/PATCH] Input: possible deadlock in i8042

[Dmitry Torokhov]

On Sunday 30 November 2003 04:00 am, Vojtech Pavlik wrote:
> On Sun, Nov 30, 2003 at 03:03:57AM -0500, Dmitry Torokhov wrote:
> > If request_irq fails in i8042_open it will call
> > serio_unregister_port, which takes serio_sem. i8042_open may be
> > called:
> >
> > serio_register_port - serio_find_dev - dev->connect
> > serio_register_device - dev->connect
> >
> > Both serio_register_port and serio_register_device take serio_sem as
> > well.
> >
> > I think that serio_{register|unregister}_port can be converted into
> > submitting requests to kseriod thus removing deadlock on the
> > serio_sem.
> >
> > The patch below is on top of serio* patches in Andrew Morton's -mm
> > tree.
>
> It's nice to avoid the deadlock this way, but I think it's not a good
> idea to make the register/unregister asynchronous - it could be a nasty
> surprise for an unsuspecting driver writer.
>

OK, you were right, it's not a good idea to convert _all_ calls to
asynchronous versions as my patch throughly screwed up module unloading.
Still, I think it is OK to export separate asynchronous versions of the
functions to be used as needed. 

The patch below implements 2 new functions, serio_register_port_delayed 
and serio_unregister_port_delayed that submit appropriate to kseriod.

The patch to convert i8042 to use it will follow shortly.

Dmitry


===================================================================


ChangeSet@1.1512, 2003-11-30 23:29:06-05:00, dtor_core@ameritech.net
  Input: Add serio_[un]register_port_delayed to allow delayed
         execution of register/unregister code (via kseriod)
         when it is not clear whether serio_sem has been taken
         or not.


 drivers/input/serio/serio.c |   38 +++++++++++++++++++++++++++++++++++---
 include/linux/serio.h       |    2 ++
 2 files changed, 37 insertions(+), 3 deletions(-)


===================================================================



diff -Nru a/drivers/input/serio/serio.c b/drivers/input/serio/serio.c
--- a/drivers/input/serio/serio.c	Mon Dec  1 01:15:33 2003
+++ b/drivers/input/serio/serio.c	Mon Dec  1 01:15:33 2003
@@ -49,8 +49,10 @@
 
 EXPORT_SYMBOL(serio_interrupt);
 EXPORT_SYMBOL(serio_register_port);
+EXPORT_SYMBOL(serio_register_port_delayed);
 EXPORT_SYMBOL(__serio_register_port);
 EXPORT_SYMBOL(serio_unregister_port);
+EXPORT_SYMBOL(serio_unregister_port_delayed);
 EXPORT_SYMBOL(__serio_unregister_port);
 EXPORT_SYMBOL(serio_register_device);
 EXPORT_SYMBOL(serio_unregister_device);
@@ -83,8 +85,10 @@
 	}
 }
 
-#define SERIO_RESCAN	1
-#define SERIO_RECONNECT	2
+#define SERIO_RESCAN		1
+#define SERIO_RECONNECT		2
+#define SERIO_REGISTER_PORT	3
+#define SERIO_UNREGISTER_PORT	4
 
 static DECLARE_WAIT_QUEUE_HEAD(serio_wait);
 static DECLARE_COMPLETION(serio_exited);
@@ -111,6 +115,14 @@
 			goto event_done;
 		
 		switch (event->type) {
+			case SERIO_REGISTER_PORT :
+				__serio_register_port(event->serio);
+				break;
+
+			case SERIO_UNREGISTER_PORT :
+				__serio_unregister_port(event->serio);
+				break;
+
 			case SERIO_RECONNECT :
 				if (event->serio->dev && event->serio->dev->reconnect)
 					if (event->serio->dev->reconnect(event->serio) == 0)
@@ -198,8 +210,18 @@
 }
 
 /*
+ * Submits register request to kseriod for subsequent execution.
+ * Can be used when it is not obvious whether the serio_sem is
+ * taken or not and when delayed execution is feasible.
+ */
+void serio_register_port_delayed(struct serio *serio)
+{
+	serio_queue_event(serio, SERIO_REGISTER_PORT);
+}
+
+/*
  * Should only be called directly if serio_sem has already been taken,
- * for example when unregistering a serio from other input device's 
+ * for example when registering a serio from other input device's 
  * connect() function.
  */
 void __serio_register_port(struct serio *serio)
@@ -213,6 +235,16 @@
 	down(&serio_sem);
 	__serio_unregister_port(serio);
 	up(&serio_sem);
+}
+
+/*
+ * Submits unregister request to kseriod for subsequent execution.
+ * Can be used when it is not obvious whether the serio_sem is
+ * taken or not and when delayed execution is feasible.
+ */
+void serio_unregister_port_delayed(struct serio *serio)
+{
+	serio_queue_event(serio, SERIO_UNREGISTER_PORT);
 }
 
 /*
diff -Nru a/include/linux/serio.h b/include/linux/serio.h
--- a/include/linux/serio.h	Mon Dec  1 01:15:33 2003
+++ b/include/linux/serio.h	Mon Dec  1 01:15:33 2003
@@ -63,8 +63,10 @@
 irqreturn_t serio_interrupt(struct serio *serio, unsigned char data, unsigned int flags, struct pt_regs *regs);
 
 void serio_register_port(struct serio *serio);
+void serio_register_port_delayed(struct serio *serio);
 void __serio_register_port(struct serio *serio);
 void serio_unregister_port(struct serio *serio);
+void serio_unregister_port_delayed(struct serio *serio);
 void __serio_unregister_port(struct serio *serio);
 void serio_register_device(struct serio_dev *dev);
 void serio_unregister_device(struct serio_dev *dev);

Re: [2.6 RFC/PATCH] Input: possible deadlock in i8042

[Dmitry Torokhov]

===================================================================


ChangeSet@1.1513, 2003-11-30 23:38:00-05:00, dtor_core@ameritech.net
  Input: Unregister port not only when there us no free IRQ
         available but also when write to control register
         failed.
  
         Use serio_unregister_port_delayed in i8042_open to
         avoid deadlock on serio_sem.
  
         Also logging moved a bit


 i8042.c |   22 +++++++++++++++-------
 1 files changed, 15 insertions(+), 7 deletions(-)


===================================================================



diff -Nru a/drivers/input/serio/i8042.c b/drivers/input/serio/i8042.c
--- a/drivers/input/serio/i8042.c	Mon Dec  1 01:15:56 2003
+++ b/drivers/input/serio/i8042.c	Mon Dec  1 01:15:56 2003
@@ -231,21 +231,29 @@
 	if (request_irq(values->irq, i8042_interrupt,
 			SA_SHIRQ, "i8042", i8042_request_irq_cookie)) {
 		printk(KERN_ERR "i8042.c: Can't get irq %d for %s, unregistering the port.\n", values->irq, values->name);
-		values->exists = 0;
-		serio_unregister_port(port);
-		return -1;
+		goto irq_fail;
 	}
 
 	i8042_ctr |= values->irqen;
 
 	if (i8042_command(&i8042_ctr, I8042_CMD_CTL_WCTR)) {
-		printk(KERN_ERR "i8042.c: Can't write CTR while opening %s.\n", values->name);
-		return -1;
+		printk(KERN_ERR "i8042.c: Can't write CTR while opening %s, unregistering the port\n", values->name);
+		goto ctr_fail;
 	}
 
 	i8042_interrupt(0, NULL, NULL);
 
 	return 0;
+
+ctr_fail:
+	i8042_ctr &= ~values->irqen;
+	free_irq(values->irq, i8042_request_irq_cookie);
+
+irq_fail:
+	values->exists = 0;
+	serio_unregister_port_delayed(port);
+
+	return -1;
 }
 
 /*
@@ -691,13 +699,13 @@
 		return -1; 
 	}
 
-	serio_register_port(port);
-
 	printk(KERN_INFO "serio: i8042 %s port at %#lx,%#lx irq %d\n",
 	       values->name,
 	       (unsigned long) I8042_DATA_REG,
 	       (unsigned long) I8042_COMMAND_REG,
 	       values->irq);
+
+	serio_register_port(port);
 
 	return 0;
 }