On Wed, Jan 18, 2017 at 01:45:55PM +0100, Michal Hocko wrote:
> On Tue 17-01-17 13:42:35, Tim Chen wrote:
> [...]
> > Logic wise, We do allow pre-emption as per cpu ptr cache->slots is
> > protected by the mutex cache->alloc_lock. We switch the
> > inappropriately used this_cpu_ptr to raw_cpu_ptr for per cpu ptr
> > access of cache->slots.
>
> OK, that looks better. I would still appreciate something like the
> following folded in
> diff --git a/include/linux/swap_slots.h b/include/linux/swap_slots.h
> index fb907346c5c6..0afe748453a7 100644
> --- a/include/linux/swap_slots.h
> +++ b/include/linux/swap_slots.h
> @@ -11,6 +11,7 @@
>
> struct swap_slots_cache {
> bool lock_initialized;
> + /* protects slots, nr, cur */
> struct mutex alloc_lock;
> swp_entry_t *slots;
> int nr;
> I've included here a patch for the comments. Thanks. Tim --->8--- From: Tim Chen <[email protected]> Date: Wed, 18 Jan 2017 09:52:28 -0800 Subject: [PATCH] mm/swap: Add comments on locks in swap_slots.h To: Andrew Morton <[email protected]> Cc: Ying Huang <[email protected]>, [email protected], [email protected], [email protected], [email protected], [email protected], Hugh Dickins <[email protected]>, Shaohua Li <[email protected]>, Minchan Kim <[email protected]>, Rik van Riel <[email protected]>, Andrea Arcangeli <[email protected]>, Kirill A . Shutemov <[email protected]>, Vladimir Davydov <[email protected]>, Johannes Weiner <[email protected]>, Michal Hocko <[email protected]>, Hillf Danton <[email protected]>, Christian Borntraeger <[email protected]>, Jonathan Corbet <[email protected]> Explains what each lock protects in swap_slots_cache structure. Signed-off-by: Tim Chen <[email protected]> --- include/linux/swap_slots.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/swap_slots.h b/include/linux/swap_slots.h index fb90734..6ef92d1 100644 --- a/include/linux/swap_slots.h +++ b/include/linux/swap_slots.h @@ -11,11 +11,11 @@ struct swap_slots_cache { bool lock_initialized; - struct mutex alloc_lock; + struct mutex alloc_lock; /* protects slots, nr, cur */ swp_entry_t *slots; int nr; int cur; - spinlock_t free_lock; + spinlock_t free_lock; /* protects slots_ret, n_ret */ swp_entry_t *slots_ret; int n_ret; }; -- 2.5.5
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