On Sun, Apr 28, 2019 at 05:25:49PM -0400, Waiman Long wrote:
> Bit 1 of sem->owner (RWSEM_ANONYMOUSLY_OWNED) is used to designate an
> anonymous owner - readers or an anonymous writer. The setting of this
> anonymous bit is used as an indicator that optimistic spinning cannot
> be done on this rwsem.
>
> With the upcoming reader optimistic spinning patches, a reader-owned
> rwsem can be spinned on for a limit period of time. We still need
> this bit to indicate a rwsem is nonspinnable, but not setting this
> bit loses its meaning that the owner is known. So rename the bit
> to RWSEM_NONSPINNABLE to clarify its meaning.
>
> This patch also fixes a DEBUG_RWSEMS_WARN_ON() bug in __up_write().
>
> Signed-off-by: Waiman Long <long...@redhat.com>
> ---
> include/linux/rwsem.h | 2 +-
> kernel/locking/rwsem.c | 43 +++++++++++++++++++++---------------------
> 2 files changed, 22 insertions(+), 23 deletions(-)
>
> diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
> index 148983e21d47..bb76e82398b2 100644
> --- a/include/linux/rwsem.h
> +++ b/include/linux/rwsem.h
> @@ -50,7 +50,7 @@ struct rw_semaphore {
> };
>
> /*
> - * Setting bit 1 of the owner field but not bit 0 will indicate
> + * Setting all bits of the owner field except bit 0 will indicate
> * that the rwsem is writer-owned with an unknown owner.
> */
> #define RWSEM_OWNER_UNKNOWN ((struct task_struct *)-2L)
As you know, I'm trying to kill that :-)
