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charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210415115624.2904-1-christian.koenig@amd.com> X-Operating-System: Linux phenom 5.7.0-1-amd64 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 15, 2021 at 01:56:23PM +0200, Christian König wrote: > To be able to switch to a spinlock and reduce lock contention in the TTM > shrinker we don't want to hold a mutex while unmapping and freeing pages > from the pool. > > But then we somehow need to prevent a race between (for example) the shrinker > trying to free pages and hotplug trying to remove the device which those pages > belong to. > > Taking and releasing the shrinker semaphore on the write side after > unmapping and freeing all pages should make sure that no shrinker is running in > paralell any more. > > Signed-off-by: Christian König > --- > include/linux/shrinker.h | 1 + > mm/vmscan.c | 10 ++++++++++ > 2 files changed, 11 insertions(+) > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > index 0f80123650e2..6b75dc372fce 100644 > --- a/include/linux/shrinker.h > +++ b/include/linux/shrinker.h > @@ -92,4 +92,5 @@ extern void register_shrinker_prepared(struct shrinker *shrinker); > extern int register_shrinker(struct shrinker *shrinker); > extern void unregister_shrinker(struct shrinker *shrinker); > extern void free_prealloced_shrinker(struct shrinker *shrinker); > +extern void sync_shrinkers(void); > #endif > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 562e87cbd7a1..46cd9c215d73 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -408,6 +408,16 @@ void unregister_shrinker(struct shrinker *shrinker) > } > EXPORT_SYMBOL(unregister_shrinker); > > +/** > + * sync_shrinker - Wait for all running shrinkers to complete. Maybe make it clear this is a barrier type thing, it wont stop shrinkers at all, just synchronize with them. Acked-by: Daniel Vetter But needs an ack from Andrew for merging through drm-misc-next before we push it there. -Daniel > + */ > +void sync_shrinkers(void) > +{ > + down_write(&shrinker_rwsem); > + up_write(&shrinker_rwsem); > +} > +EXPORT_SYMBOL(sync_shrinkers); > + > #define SHRINK_BATCH 128 > > static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > -- > 2.25.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch