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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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