From: Rusty Russell <ru...@rustcorp.com.au> The previous patch added one potential problem: we can still be reading from a hwrng when it's unregistered. Add a wait for zero in the hwrng_unregister path.
v4: add cleanup_done flag to insure that cleanup is done Signed-off-by: Rusty Russell <ru...@rustcorp.com.au> Signed-off-by: Amos Kong <ak...@redhat.com> --- drivers/char/hw_random/core.c | 8 ++++++++ include/linux/hw_random.h | 1 + 2 files changed, 9 insertions(+) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 27ad6b4..c31bf91 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -60,6 +60,7 @@ 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" */ @@ -98,6 +99,8 @@ static inline void cleanup_rng(struct kref *kref) if (rng->cleanup) rng->cleanup(rng); + rng->cleanup_done = true; + wake_up_all(&rng_done); } static void set_current_rng(struct hwrng *rng) @@ -536,6 +539,11 @@ void hwrng_unregister(struct hwrng *rng) kthread_stop(hwrng_fill); } 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); + } EXPORT_SYMBOL_GPL(hwrng_unregister); diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h index c212e71..7832e50 100644 --- a/include/linux/hw_random.h +++ b/include/linux/hw_random.h @@ -46,6 +46,7 @@ struct hwrng { /* internal. */ struct list_head list; struct kref ref; + bool cleanup_done; }; /** Register a new Hardware Random Number Generator driver. */ -- 1.9.3 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization