Hi Matthew,
Sorry I missed this, I'm over on @kernel.org now and don't have access to
my old @arm.com address anymore.
On Thu, Mar 26, 2020 at 05:24:28AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
>
> This local definition hasn't been used since commit 84c6591103db
> ("locking/atomics, asm-generic/bitops/lock.h: Rewrite using
> atomic_fetch_*()") which provided a default definition.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> ---
> mm/filemap.c | 23 -----------------------
> 1 file changed, 23 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 80f7e1ae744c..312afbfcb49a 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1248,29 +1248,6 @@ void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
> }
> EXPORT_SYMBOL_GPL(add_page_wait_queue);
>
> -#ifndef clear_bit_unlock_is_negative_byte
> -
> -/*
> - * PG_waiters is the high bit in the same byte as PG_lock.
> - *
> - * On x86 (and on many other architectures), we can clear PG_lock and
> - * test the sign bit at the same time. But if the architecture does
> - * not support that special operation, we just do this all by hand
> - * instead.
> - *
> - * The read of PG_waiters has to be after (or concurrently with) PG_locked
> - * being cleared, but a memory barrier should be unneccssary since it is
> - * in the same byte as PG_locked.
> - */
> -static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
> -{
> - clear_bit_unlock(nr, mem);
> - /* smp_mb__after_atomic(); */
> - return test_bit(PG_waiters, mem);
> -}
> -
> -#endif
> -
I'd really like to do this, but I worry that the generic definition still
isn't available on all architectures depending on how they pull together
their bitops.h. Have you tried building for alpha or s390? At a quick
glance, they look like they might fall apart :(
Will
