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    Subject[PATCH] make attribute_container_unregister() unconditionally wait for list empty
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    James,

    >> > > Isn't a better way to handle it simply to give
    >> > > transport_container_unregister() the semantics everyone is expecting
    >> > > (i.e. to wait for everything to be tidied up and gone)? That way none
    >> > > of the transport classes needs updating, and we don't have to handle the
    >> > > rather nasty release and unload races.
    >
    > I was thinking of a wait_event driven system checking for
    > list_empty(cont->containers.k_list)

    I hope this is more in line with what you were thinking.....

    -- james s


    Signed-off-by: James Smart <James.Smart@emulex.com>


    diff -upNr a/drivers/base/attribute_container.c b/drivers/base/attribute_container.c
    --- a/drivers/base/attribute_container.c 2007-08-16 02:59:50.000000000 -0400
    +++ b/drivers/base/attribute_container.c 2007-08-17 05:02:03.000000000 -0400
    @@ -19,6 +19,7 @@
    #include <linux/list.h>
    #include <linux/module.h>
    #include <linux/mutex.h>
    +#include <linux/sched.h>

    #include "base.h"

    @@ -75,6 +76,8 @@ int
    attribute_container_register(struct attribute_container *cont)
    {
    INIT_LIST_HEAD(&cont->node);
    + init_waitqueue_head(&cont->cont_wait);
    + cont->flags &= ~ATTRIBUTE_CONTAINER_EVENT_PENDING;
    klist_init(&cont->containers,internal_container_klist_get,
    internal_container_klist_put);

    @@ -89,23 +92,26 @@ EXPORT_SYMBOL_GPL(attribute_container_re
    /**
    * attribute_container_unregister - remove a container registration
    *
    + * Semantics have now changed - we never return until the list goes empty
    + *
    * @cont: previously registered container to remove
    */
    int
    attribute_container_unregister(struct attribute_container *cont)
    {
    - int retval = -EBUSY;
    mutex_lock(&attribute_container_mutex);
    spin_lock(&cont->containers.k_lock);
    - if (!list_empty(&cont->containers.k_list))
    - goto out;
    - retval = 0;
    - list_del(&cont->node);
    - out:
    + if (!list_empty(&cont->containers.k_list))
    + cont->flags |= ATTRIBUTE_CONTAINER_EVENT_PENDING;
    spin_unlock(&cont->containers.k_lock);
    mutex_unlock(&attribute_container_mutex);
    - return retval;
    -
    + wait_event(cont->cont_wait,
    + !(cont->flags & ATTRIBUTE_CONTAINER_EVENT_PENDING));
    + mutex_lock(&attribute_container_mutex);
    + list_del(&cont->node);
    + mutex_unlock(&attribute_container_mutex);
    +
    + return 0;
    }
    EXPORT_SYMBOL_GPL(attribute_container_unregister);

    @@ -234,6 +240,15 @@ attribute_container_remove_device(struct
    class_device_unregister(&ic->classdev);
    }
    }
    +
    + if (cont->flags & ATTRIBUTE_CONTAINER_EVENT_PENDING) {
    + spin_lock(&cont->containers.k_lock);
    + if (list_empty(&cont->containers.k_list))
    + cont->flags &=
    + ~ATTRIBUTE_CONTAINER_EVENT_PENDING;
    + spin_unlock(&cont->containers.k_lock);
    + wake_up(&cont->cont_wait);
    + }
    }
    mutex_unlock(&attribute_container_mutex);
    }
    diff -upNr a/include/linux/attribute_container.h b/include/linux/attribute_container.h
    --- a/include/linux/attribute_container.h 2007-08-16 03:00:10.000000000 -0400
    +++ b/include/linux/attribute_container.h 2007-08-17 03:46:01.000000000 -0400
    @@ -20,7 +20,9 @@ struct attribute_container {
    struct class_device_attribute **attrs;
    int (*match)(struct attribute_container *, struct device *);
    #define ATTRIBUTE_CONTAINER_NO_CLASSDEVS 0x01
    +#define ATTRIBUTE_CONTAINER_EVENT_PENDING 0x02
    unsigned long flags;
    + wait_queue_head_t cont_wait;
    };

    static inline int


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