Message ID | 20231029230205.93277-22-dmitry.osipenko@collabora.com |
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State | New |
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(109-252-153-31.dynamic.spd-mgts.ru [109.252.153.31]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by madras.collabora.co.uk (Postfix) with ESMTPSA id D51C766073AE; Sun, 29 Oct 2023 23:02:56 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1698620578; bh=wqGvYp+XsBubezC7g24J4y9IRLkJRkmLc/LBzEkyYBg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WOwYdYKjt/I83fqDDsTMg5Buu1wHFIkeuyU9wAcSaZy3NfTy6QueCldxukReDXMo3 KBPvD83s9Glkx/p+53DWqpsQHJm+S0ci8yNyxTwamtrjRvAFIQz0FU6NOPJe6sJzsb cSuipy3uuEDuZgiK4toXK1IG6qQBdkNeIGgNjnj57QkEtNdzrsm93/1UBbgpAVAdjX Lot0g4ZFK+tKMsJLbrn+6DzBWbCp0cW9/2Jt5leAiGDM91fUu6C5b4afwkU8AQBY0a YECMj0VIWnka9VVDcHBwwap2dQUuNs2oJc+meDtl3mrAoSYWUeQUhvf8k1DRoHIEI1 jZWv4n6jSLZrw== From: Dmitry Osipenko <dmitry.osipenko@collabora.com> To: David Airlie <airlied@gmail.com>, Gerd Hoffmann <kraxel@redhat.com>, Gurchetan Singh <gurchetansingh@chromium.org>, Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>, Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>, =?utf-8?q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>, Qiang Yu <yuq825@gmail.com>, Steven Price <steven.price@arm.com>, Boris Brezillon <boris.brezillon@collabora.com>, Emma Anholt <emma@anholt.net>, Melissa Wen <mwen@igalia.com> Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, virtualization@lists.linux-foundation.org Subject: [PATCH v18 21/26] drm/shmem-helper: Optimize unlocked get_pages_sgt() Date: Mon, 30 Oct 2023 02:02:00 +0300 Message-ID: <20231029230205.93277-22-dmitry.osipenko@collabora.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231029230205.93277-1-dmitry.osipenko@collabora.com> References: <20231029230205.93277-1-dmitry.osipenko@collabora.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-0.8 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Sun, 29 Oct 2023 16:19:40 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1781133824634479157 X-GMAIL-MSGID: 1781133824634479157 |
Series |
Add generic memory shrinker to VirtIO-GPU and Panfrost DRM drivers
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Commit Message
Dmitry Osipenko
Oct. 29, 2023, 11:02 p.m. UTC
SGT isn't refcounted. Once SGT pointer has been obtained, it remains the
same for both locked and unlocked get_pages_sgt(). Return cached SGT
directly without taking a potentially expensive lock.
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 3 +++
1 file changed, 3 insertions(+)
Comments
On Mon, 30 Oct 2023 02:02:00 +0300 Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote: > SGT isn't refcounted. Once SGT pointer has been obtained, it remains the > same for both locked and unlocked get_pages_sgt(). Return cached SGT > directly without taking a potentially expensive lock. > > Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 560ce565f376..6dd087f19ea3 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -955,6 +955,9 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem) > drm_WARN_ON(obj->dev, drm_gem_shmem_is_evictable(shmem)); > drm_WARN_ON(obj->dev, drm_gem_shmem_is_purgeable(shmem)); > > + if (shmem->sgt) > + return shmem->sgt; > + By doing that, you introduce a race between drm_gem_shmem_put_pages() and drm_gem_shmem_get_pages_sgt(). I know it's only happening if the user doesn't follow the rule listed in drm_gem_shmem_get_pages_sgt() doc (caller must owns a pages ref before calling drm_gem_shmem_get_pages_sgt()), but now you return a possibly invalid pointer instead of returning an error when this happens. If that's what we want, we should at least update the documentation to make it clear. > ret = dma_resv_lock_interruptible(shmem->base.resv, NULL); > if (ret) > return ERR_PTR(ret);
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 560ce565f376..6dd087f19ea3 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -955,6 +955,9 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem) drm_WARN_ON(obj->dev, drm_gem_shmem_is_evictable(shmem)); drm_WARN_ON(obj->dev, drm_gem_shmem_is_purgeable(shmem)); + if (shmem->sgt) + return shmem->sgt; + ret = dma_resv_lock_interruptible(shmem->base.resv, NULL); if (ret) return ERR_PTR(ret);