Message ID | 20240105184624.508603-16-dmitry.osipenko@collabora.com |
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State | New |
Headers |
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(cola.collaboradmins.com [195.201.22.229]) (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 madrid.collaboradmins.com (Postfix) with ESMTPSA id 37097378203D; Fri, 5 Jan 2024 18:47:07 +0000 (UTC) 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 v19 15/30] drm/shmem-helper: Avoid lockdep warning when pages are released Date: Fri, 5 Jan 2024 21:46:09 +0300 Message-ID: <20240105184624.508603-16-dmitry.osipenko@collabora.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240105184624.508603-1-dmitry.osipenko@collabora.com> References: <20240105184624.508603-1-dmitry.osipenko@collabora.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: <linux-kernel.vger.kernel.org> List-Subscribe: <mailto:linux-kernel+subscribe@vger.kernel.org> List-Unsubscribe: <mailto:linux-kernel+unsubscribe@vger.kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1787277520150007462 X-GMAIL-MSGID: 1787277520150007462 |
Series |
Add generic memory shrinker to VirtIO-GPU and Panfrost DRM drivers
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Commit Message
Dmitry Osipenko
Jan. 5, 2024, 6:46 p.m. UTC
All drivers will be moved to get/put pages explicitly and then the last
put_pages() will be invoked during gem_free() time by some drivers.
We can't touch reservation lock when GEM is freed because that will cause
a spurious warning from lockdep when shrinker support will be added.
Lockdep doesn't know that fs_reclaim isn't functioning for a freed object,
and thus, can't deadlock. Release pages directly without taking reservation
lock if GEM is freed and its refcount is zero.
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
Comments
On Fri, 5 Jan 2024 21:46:09 +0300 Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote: > All drivers will be moved to get/put pages explicitly and then the last > put_pages() will be invoked during gem_free() time by some drivers. > We can't touch reservation lock when GEM is freed because that will cause > a spurious warning from lockdep when shrinker support will be added. > Lockdep doesn't know that fs_reclaim isn't functioning for a freed object, > and thus, can't deadlock. Release pages directly without taking reservation > lock if GEM is freed and its refcount is zero. > > Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index f5ed64f78648..c7357110ca76 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -242,6 +242,22 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem) > if (refcount_dec_not_one(&shmem->pages_use_count)) > return; > > + /* > + * Destroying the object is a special case because acquiring > + * the obj lock can cause a locking order inversion between > + * reservation_ww_class_mutex and fs_reclaim. > + * > + * This deadlock is not actually possible, because no one should > + * be already holding the lock when GEM is released. Unfortunately > + * lockdep is not aware of this detail. So when the refcount drops > + * to zero, we pretend it is already locked. > + */ > + if (!kref_read(&shmem->base.refcount)) { > + if (refcount_dec_and_test(&shmem->pages_use_count)) > + drm_gem_shmem_free_pages(shmem); > + return; > + } > + > dma_resv_lock(shmem->base.resv, NULL); > drm_gem_shmem_put_pages_locked(shmem); > dma_resv_unlock(shmem->base.resv);
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index f5ed64f78648..c7357110ca76 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -242,6 +242,22 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem) if (refcount_dec_not_one(&shmem->pages_use_count)) return; + /* + * Destroying the object is a special case because acquiring + * the obj lock can cause a locking order inversion between + * reservation_ww_class_mutex and fs_reclaim. + * + * This deadlock is not actually possible, because no one should + * be already holding the lock when GEM is released. Unfortunately + * lockdep is not aware of this detail. So when the refcount drops + * to zero, we pretend it is already locked. + */ + if (!kref_read(&shmem->base.refcount)) { + if (refcount_dec_and_test(&shmem->pages_use_count)) + drm_gem_shmem_free_pages(shmem); + return; + } + dma_resv_lock(shmem->base.resv, NULL); drm_gem_shmem_put_pages_locked(shmem); dma_resv_unlock(shmem->base.resv);