Re: [PATCH] ipc 1/3: Add refcount to ipc_rcu_alloc

[Andrew Morton]

Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> wrote:
>
> the lifetime of the ipc objects (sem array, msg queue, shm mapping) is 
>  controlled by kern_ipc_perms->lock - a spinlock. There is no simple way 
>  to reacquire this spinlock after it was dropped to 
>  schedule()/kmalloc/copy_{to,from}_user/whatever.
> 
>  The attached patch adds a reference count as a preparation to get rid of 
>  sem_revalidate().

The pointer offsetting tricks are rather unattractive.  Is it not possible
to simple aggregate the refcount into the refcounted structure, use
container_of()?

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