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SubjectRe: [PATCH 7/7] driver-core : convert semaphore to mutex in struct class
On Jan 15, 2008 9:56 PM, Jarek Poplawski <jarkao2@gmail.com> wrote:
>
> On Tue, Jan 15, 2008 at 05:15:27PM +0800, Dave Young wrote:
> > Convert the class semaphore to mutex.
> >
> > Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
> >
> > ---
> > drivers/base/class.c | 38 +++++++++++++++++++-------------------
> > drivers/base/core.c | 18 ++++++++----------
> > include/linux/device.h | 3 ++-
> > 3 files changed, 29 insertions(+), 30 deletions(-)
> >
> > diff -upr linux/drivers/base/class.c linux.new/drivers/base/class.c
> > --- linux/drivers/base/class.c 2008-01-15 14:04:26.000000000 +0800
> > +++ linux.new/drivers/base/class.c 2008-01-15 14:04:26.000000000 +0800
> > @@ -144,7 +144,7 @@ int class_register(struct class * cls)
> > INIT_LIST_HEAD(&cls->devices);
> > INIT_LIST_HEAD(&cls->interfaces);
> > kset_init(&cls->class_dirs);
> > - init_MUTEX(&cls->sem);
> > + mutex_init(&cls->mutex);
> > error = kobject_set_name(&cls->subsys.kobj, "%s", cls->name);
> > if (error)
> > return error;
> > @@ -617,13 +617,13 @@ int class_device_add(struct class_device
> > kobject_uevent(&class_dev->kobj, KOBJ_ADD);
> >
> > /* notify any interfaces this device is now here */
> > - down(&parent_class->sem);
> > + mutex_lock_nested(&parent_class->mutex, SINGLE_DEPTH_NESTING);
> > list_add_tail(&class_dev->node, &parent_class->children);
> > list_for_each_entry(class_intf, &parent_class->interfaces, node) {
> > if (class_intf->add)
> > class_intf->add(class_dev, class_intf);
> > }
> > - up(&parent_class->sem);
> > + mutex_unlock(&parent_class->mutex);
> >
> > goto out1;
> >
> > @@ -725,12 +725,12 @@ void class_device_del(struct class_devic
> > struct class_interface *class_intf;
> >
> > if (parent_class) {
> > - down(&parent_class->sem);
> > + mutex_lock(&parent_class->mutex);
>
> I hope I'm wrong with this (I don't know this code at all...), and
> of course I should've noticed this earlier after all, but I wonder
> about this _NESTING corretness here. So, if these variables names
> are right, and say about real nesting dependency, then it seems
> mutex_lock_nested() should be used consistently even if (currently?)
> not forced by lockdep warnings; otherwise this could possibly cover
> some other warnings. Alas, if accidentally I'm right, it seems a
> bit of new testing would be necessary...

The lockdep warining was posted in the below thread, actually, I have
built and run this patced kernel for several days, there's no more
warnings.
http://lkml.org/lkml/2008/1/3/2

>
> Regards,
> Jarek P.
>


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