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Thu, 15 Apr 2021 06:23:46 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id u14sm3290214wrq.65.2021.04.15.06.23.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Apr 2021 06:23:45 -0700 (PDT) Date: Thu, 15 Apr 2021 15:23:43 +0200 From: Daniel Vetter To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, vbabka@suse.cz, daniel@ffwll.ch, ray.huang@amd.com, akpm@linux-foundation.org Subject: Re: [PATCH 1/2] mm/vmscan: add sync_shrinkers function Message-ID: Mail-Followup-To: Christian =?iso-8859-1?Q?K=F6nig?= , linux-mm@kvack.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, vbabka@suse.cz, ray.huang@amd.com, akpm@linux-foundation.org References: <20210415115624.2904-1-christian.koenig@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20210415115624.2904-1-christian.koenig@amd.com> X-Operating-System: Linux phenom 5.7.0-1-amd64 X-Rspamd-Queue-Id: DD8A2200027E X-Stat-Signature: ftb81pri51wpk4hciq3hk16ea4nkbasx X-Rspamd-Server: rspam02 Received-SPF: none (ffwll.ch>: No applicable sender policy available) receiver=imf11; identity=mailfrom; envelope-from=""; helo=mail-wr1-f42.google.com; client-ip=209.85.221.42 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618493017-616284 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Apr 15, 2021 at 01:56:23PM +0200, Christian K=F6nig wrote: > To be able to switch to a spinlock and reduce lock contention in the TT= M > shrinker we don't want to hold a mutex while unmapping and freeing page= s > from the pool. >=20 > But then we somehow need to prevent a race between (for example) the sh= rinker > trying to free pages and hotplug trying to remove the device which thos= e pages > belong to. >=20 > Taking and releasing the shrinker semaphore on the write side after > unmapping and freeing all pages should make sure that no shrinker is ru= nning in > paralell any more. >=20 > Signed-off-by: Christian K=F6nig > --- > include/linux/shrinker.h | 1 + > mm/vmscan.c | 10 ++++++++++ > 2 files changed, 11 insertions(+) >=20 > 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 shrinke= r *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); > =20 > +/** > + * 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 > =20 > static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > --=20 > 2.25.1 >=20 --=20 Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch