Messages in this thread | | | Date | Wed, 16 Aug 2023 11:14:31 +0200 | Subject | Re: [PATCH 4/5] drm/ttm: introduce pool_shrink_rwsem | From | Christian König <> |
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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 <zhengqi.arch@bytedance.com> > Reviewed-by: Muchun Song <songmuchun@bytedance.com> > --- > 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 <christian.koenig@amd.com>
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);
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