On Wed, Jul 22, 2015 at 11:15:35PM +0200, Oleg Nesterov wrote:
> Add percpu_rwsem_release() and percpu_rwsem_acquire() for the users
> which need to return to userspace with percpu-rwsem lock held and/or
> pass the ownership to another thread.
>
> TODO: change percpu_rwsem_release() to use rwsem_clear_owner(). We can
> either fold kernel/locking/rwsem.h into include/linux/rwsem.h, or add
> the non-inline percpu_rwsem_clear_owner().
>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> ---
> include/linux/percpu-rwsem.h | 19 +++++++++++++++++++
> 1 files changed, 19 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
> index 3ebf982..06af654 100644
> --- a/include/linux/percpu-rwsem.h
> +++ b/include/linux/percpu-rwsem.h
> @@ -33,4 +33,23 @@ extern void percpu_free_rwsem(struct percpu_rw_semaphore *);
> __percpu_init_rwsem(brw, #brw, &rwsem_key); \
> })
>
> +
> +#define percpu_rwsem_is_held(sem) lockdep_is_held(&(sem)->rw_sem)
> +
> +static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem,
> + bool read, unsigned long ip)
> +{
> + lock_release(&sem->rw_sem.dep_map, 1, ip);
> +#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
> + if (!read)
> + sem->rw_sem.owner = NULL;
> +#endif
> +}
> +
> +static inline void percpu_rwsem_acquire(struct percpu_rw_semaphore *sem,
> + bool read, unsigned long ip)
> +{
> + lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
> +}
This is of course entirely vile.. Can't we open code that in the freezer
code? Having helpers here might give some people the impression that
this is a sane thing to do.
Also, when you do that in the freezer, put a big honking comment on it.
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