Re: [PATCH 1/5] hwrng: core - Use struct completion for cleanup_done

Rusty Russell
2014-12-26T00:31:18Z

Herbert Xu <herbert@gondor.apana.org.au> writes:
> There is no point in doing a manual completion for cleanup_done
> when struct completion fits in perfectly.
>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Indeed.

Acked-by: Rusty Russell <rusty@rustcorp.com.au>

Thanks,
Rusty.

> ---
>
> drivers/char/hw_random/core.c | 12 +++---------
> include/linux/hw_random.h | 3 ++-
> 2 files changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index 6ec4225..3dba2cf 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -60,7 +60,6 @@ static DEFINE_MUTEX(rng_mutex);
> static DEFINE_MUTEX(reading_mutex);
> static int data_avail;
> static u8 *rng_buffer, *rng_fillbuf;
> -static DECLARE_WAIT_QUEUE_HEAD(rng_done);
> static unsigned short current_quality;
> static unsigned short default_quality; /* = 0; default to "off" */
>
> @@ -100,10 +99,7 @@ static inline void cleanup_rng(struct kref *kref)
> if (rng->cleanup)
> rng->cleanup(rng);
>
> - /* cleanup_done should be updated after cleanup finishes */
> - smp_wmb();
> - rng->cleanup_done = true;
> - wake_up_all(&rng_done);
> + complete(&rng->cleanup_done);
> }
>
> static void set_current_rng(struct hwrng *rng)
> @@ -498,7 +494,7 @@ int hwrng_register(struct hwrng *rng)
> add_early_randomness(rng);
> }
>
> - rng->cleanup_done = false;
> + init_completion(&rng->cleanup_done);
>
> out_unlock:
> mutex_unlock(&rng_mutex);
> @@ -532,9 +528,7 @@ void hwrng_unregister(struct hwrng *rng)
> } else
> mutex_unlock(&rng_mutex);
>
> - /* Just in case rng is reading right now, wait. */
> - wait_event(rng_done, rng->cleanup_done &&
> - atomic_read(&rng->ref.refcount) == 0);
> + wait_for_completion(&rng->cleanup_done);
> }
> EXPORT_SYMBOL_GPL(hwrng_unregister);
>
> diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
> index 7832e50..eb7b414 100644
> --- a/include/linux/hw_random.h
> +++ b/include/linux/hw_random.h
> @@ -12,6 +12,7 @@
> #ifndef LINUX_HWRANDOM_H_
> #define LINUX_HWRANDOM_H_
>
> +#include <linux/completion.h>
> #include <linux/types.h>
> #include <linux/list.h>
> #include <linux/kref.h>
> @@ -46,7 +47,7 @@ struct hwrng {
> /* internal. */
> struct list_head list;
> struct kref ref;
> - bool cleanup_done;
> + struct completion cleanup_done;
> };
>
> /** Register a new Hardware Random Number Generator driver. */