Am 16.08.23 um 10:34 schrieb Qi Zheng:
> Currently, the synchronize_shrinkers() is only used by TTM pool. It only
> requires that no shrinkers run in parallel.
>
> After we use RCU+refcount method to implement the lockless slab shrink,
> we can not use shrinker_rwsem or synchronize_rcu() to guarantee that all
> shrinker invocations have seen an update before freeing memory.
>
> So we introduce a new pool_shrink_rwsem to implement a private
> synchronize_shrinkers(), so as to achieve the same purpose.
>
> Signed-off-by: Qi Zheng <[email protected]>
> Reviewed-by: Muchun Song <[email protected]>
> ---
> drivers/gpu/drm/ttm/ttm_pool.c | 15 +++++++++++++++
> include/linux/shrinker.h | 1 -
> mm/shrinker.c | 15 ---------------
> 3 files changed, 15 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index cddb9151d20f..713b1c0a70e1 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -74,6 +74,7 @@ static struct ttm_pool_type global_dma32_uncached[MAX_ORDER + 1];
> static spinlock_t shrinker_lock;
> static struct list_head shrinker_list;
> static struct shrinker mm_shrinker;
> +static DECLARE_RWSEM(pool_shrink_rwsem);
>
> /* Allocate pages of size 1 << order with the given gfp_flags */
> static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags,
> @@ -317,6 +318,7 @@ static unsigned int ttm_pool_shrink(void)
> unsigned int num_pages;
> struct page *p;
>
> + down_read(&pool_shrink_rwsem);
> spin_lock(&shrinker_lock);
> pt = list_first_entry(&shrinker_list, typeof(*pt), shrinker_list);
> list_move_tail(&pt->shrinker_list, &shrinker_list);
> @@ -329,6 +331,7 @@ static unsigned int ttm_pool_shrink(void)
> } else {
> num_pages = 0;
> }
> + up_read(&pool_shrink_rwsem);
>
> return num_pages;
> }
> @@ -572,6 +575,18 @@ void ttm_pool_init(struct ttm_pool *pool, struct device *dev,
> }
> EXPORT_SYMBOL(ttm_pool_init);
>
> +/**
> + * synchronize_shrinkers - Wait for all running shrinkers to complete.
> + *
> + * This is useful to guarantee that all shrinker invocations have seen an
> + * update, before freeing memory, similar to rcu.
> + */
> +static void synchronize_shrinkers(void)
Please rename that function to ttm_pool_synchronize_shrinkers().
With that done feel free to add Reviewed-by: Christian König
<[email protected]>
Regards,
Christian.
> +{
> + down_write(&pool_shrink_rwsem);
> + up_write(&pool_shrink_rwsem);
> +}
> +
> /**
> * ttm_pool_fini - Cleanup a pool
> *
> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index 8dc15aa37410..6b5843c3b827 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -103,7 +103,6 @@ extern int __printf(2, 3) register_shrinker(struct shrinker *shrinker,
> const char *fmt, ...);
> extern void unregister_shrinker(struct shrinker *shrinker);
> extern void free_prealloced_shrinker(struct shrinker *shrinker);
> -extern void synchronize_shrinkers(void);
>
> #ifdef CONFIG_SHRINKER_DEBUG
> extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker *shrinker,
> diff --git a/mm/shrinker.c b/mm/shrinker.c
> index 043c87ccfab4..a16cd448b924 100644
> --- a/mm/shrinker.c
> +++ b/mm/shrinker.c
> @@ -692,18 +692,3 @@ void unregister_shrinker(struct shrinker *shrinker)
> shrinker->nr_deferred = NULL;
> }
> EXPORT_SYMBOL(unregister_shrinker);
> -
> -/**
> - * synchronize_shrinkers - Wait for all running shrinkers to complete.
> - *
> - * This is equivalent to calling unregister_shrink() and register_shrinker(),
> - * but atomically and with less overhead. This is useful to guarantee that all
> - * shrinker invocations have seen an update, before freeing memory, similar to
> - * rcu.
> - */
> -void synchronize_shrinkers(void)
> -{
> - down_write(&shrinker_rwsem);
> - up_write(&shrinker_rwsem);
> -}
> -EXPORT_SYMBOL(synchronize_shrinkers);