[patch] i2c: fix virtual i2c adapter lockdep warning

[patch] i2c: fix virtual i2c adapter lockdep warning

[David Rientjes]

bus_lock for both the virtual adapter and its parent have the same lock
class.  Since both are taken in i2c_virt_master_xfer() and
i2c_virt_smbus_xfer(), lockdep needs an annotation that the nesting is
safe.

Signed-off-by: David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
---
 drivers/i2c/i2c-virt.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/i2c-virt.c b/drivers/i2c/i2c-virt.c
--- a/drivers/i2c/i2c-virt.c
+++ b/drivers/i2c/i2c-virt.c
@@ -53,7 +53,7 @@ static int i2c_virt_master_xfer(struct i2c_adapter *adap,
 	 * the transfer.
 	 */
 
-	mutex_lock(&parent->bus_lock);
+	mutex_lock_nested(&parent->bus_lock, SINGLE_DEPTH_NESTING);
 
 	ret = priv->select(parent, priv->client, priv->id);
 	if (ret >= 0)
@@ -79,7 +79,7 @@ static int i2c_virt_smbus_xfer(struct i2c_adapter *adap,
 	 * the transfer.
 	 */
 
-	mutex_lock(&parent->bus_lock);
+	mutex_lock_nested(&parent->bus_lock, SINGLE_DEPTH_NESTING);
 
 	ret = priv->select(parent, priv->client, priv->id);
 	if (ret == 0)

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Re: [patch] i2c: fix virtual i2c adapter lockdep warning

[Rodolfo Giometti]

On Mon, Aug 04, 2008 at 10:50:42AM -0700, David Rientjes wrote:
> bus_lock for both the virtual adapter and its parent have the same lock
> class.  Since both are taken in i2c_virt_master_xfer() and
> i2c_virt_smbus_xfer(), lockdep needs an annotation that the nesting is
> safe.

Thanks! This nested lock can be used also to remove to nolock
functions into i2c-core.c?

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail: giometti-AVVDYK/kqiJWk0Htik3J/w@public.gmane.org
Linux Device Driver                          giometti-k2GhghHVRtY@public.gmane.org
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UNIX programming                     skype:  rodolfo.giometti

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Re: [patch] i2c: fix virtual i2c adapter lockdep warning

[David Rientjes]

On Thu, 14 Aug 2008, Rodolfo Giometti wrote:

> Thanks! This nested lock can be used also to remove to nolock
> functions into i2c-core.c?
> 

I haven't looked at i2c-core.c specifically, but you can nest to 
SINGLE_DEPTH_NESTING anytime you are sure that two mutexes of the same 
lock class are taken inside each other and its impossible that they are 
actually the exact same lock.

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