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Message-ID: <5ec9313e-8498-2838-0320-331c347ce905@amd.com>
Date: Fri, 15 Jul 2022 08:50:22 +0200
From: Christian König <christian.koenig@....com>
To: Dmitry Osipenko <dmitry.osipenko@...labora.com>,
David Airlie <airlied@...ux.ie>,
Gerd Hoffmann <kraxel@...hat.com>,
Gurchetan Singh <gurchetansingh@...omium.org>,
Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
Daniel Almeida <daniel.almeida@...labora.com>,
Gert Wollny <gert.wollny@...labora.com>,
Gustavo Padovan <gustavo.padovan@...labora.com>,
Daniel Stone <daniel@...ishbar.org>,
Tomeu Vizoso <tomeu.vizoso@...labora.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
Rob Clark <robdclark@...il.com>,
Sumit Semwal <sumit.semwal@...aro.org>,
"Pan, Xinhui" <Xinhui.Pan@....com>,
Thierry Reding <thierry.reding@...il.com>,
Tomasz Figa <tfiga@...omium.org>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Alex Deucher <alexander.deucher@....com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
Thomas Hellström <thomas_os@...pmail.org>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Dmitry Osipenko <digetx@...il.com>,
linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
amd-gfx@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
kernel@...labora.com, virtualization@...ts.linux-foundation.org,
spice-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v1 4/6] dma-buf: Acquire wait-wound context on attachment
Am 15.07.22 um 02:52 schrieb Dmitry Osipenko:
> Intel i915 GPU driver uses wait-wound mutex to lock multiple GEMs on the
> attachment to the i915 dma-buf. In order to let all drivers utilize shared
> wait-wound context during attachment in a general way, make dma-buf core to
> acquire the ww context internally for the attachment operation and update
> i915 driver to use the importer's ww context instead of the internal one.
>
> From now on all dma-buf exporters shall use the importer's ww context for
> the attachment operation.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> ---
> drivers/dma-buf/dma-buf.c | 8 +++++-
> drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 2 +-
> .../gpu/drm/i915/gem/i915_gem_execbuffer.c | 2 +-
> drivers/gpu/drm/i915/gem/i915_gem_object.h | 6 ++---
> drivers/gpu/drm/i915/i915_gem_evict.c | 2 +-
> drivers/gpu/drm/i915/i915_gem_ww.c | 26 +++++++++++++++----
> drivers/gpu/drm/i915/i915_gem_ww.h | 15 +++++++++--
> 7 files changed, 47 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 0ee588276534..37545ecb845a 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -807,6 +807,8 @@ static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach,
> * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
> * functionality.
> *
> + * Exporters shall use ww_ctx acquired by this function.
> + *
> * Returns:
> *
> * A pointer to newly created &dma_buf_attachment on success, or a negative
> @@ -822,6 +824,7 @@ dma_buf_dynamic_attach_unlocked(struct dma_buf *dmabuf, struct device *dev,
> void *importer_priv)
> {
> struct dma_buf_attachment *attach;
> + struct ww_acquire_ctx ww_ctx;
> int ret;
>
> if (WARN_ON(!dmabuf || !dev))
> @@ -841,7 +844,8 @@ dma_buf_dynamic_attach_unlocked(struct dma_buf *dmabuf, struct device *dev,
> attach->importer_ops = importer_ops;
> attach->importer_priv = importer_priv;
>
> - dma_resv_lock(dmabuf->resv, NULL);
> + ww_acquire_init(&ww_ctx, &reservation_ww_class);
> + dma_resv_lock(dmabuf->resv, &ww_ctx);
That won't work like this. The core property of a WW context is that you
need to unwind all the locks and re-quire them with the contended one first.
When you statically lock the imported one here you can't do that any more.
Regards,
Christian.
>
> if (dmabuf->ops->attach) {
> ret = dmabuf->ops->attach(dmabuf, attach);
> @@ -876,11 +880,13 @@ dma_buf_dynamic_attach_unlocked(struct dma_buf *dmabuf, struct device *dev,
> }
>
> dma_resv_unlock(dmabuf->resv);
> + ww_acquire_fini(&ww_ctx);
>
> return attach;
>
> err_attach:
> dma_resv_unlock(attach->dmabuf->resv);
> + ww_acquire_fini(&ww_ctx);
> kfree(attach);
> return ERR_PTR(ret);
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> index c199bf71c373..9173f0232b16 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> @@ -173,7 +173,7 @@ static int i915_gem_dmabuf_attach(struct dma_buf *dmabuf,
> if (!i915_gem_object_can_migrate(obj, INTEL_REGION_SMEM))
> return -EOPNOTSUPP;
>
> - for_i915_gem_ww(&ww, err, true) {
> + for_i915_dmabuf_ww(&ww, dmabuf, err, true) {
> err = i915_gem_object_migrate(obj, &ww, INTEL_REGION_SMEM);
> if (err)
> continue;
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index 30fe847c6664..ad7d602fc43a 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -3409,7 +3409,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
> goto err_vma;
> }
>
> - ww_acquire_done(&eb.ww.ctx);
> + ww_acquire_done(eb.ww.ctx);
> eb_capture_stage(&eb);
>
> out_fence = eb_requests_create(&eb, in_fence, out_fence_fd);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> index e11d82a9f7c3..5ae38f94a5c7 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> @@ -178,9 +178,9 @@ static inline int __i915_gem_object_lock(struct drm_i915_gem_object *obj,
> int ret;
>
> if (intr)
> - ret = dma_resv_lock_interruptible(obj->base.resv, ww ? &ww->ctx : NULL);
> + ret = dma_resv_lock_interruptible(obj->base.resv, ww ? ww->ctx : NULL);
> else
> - ret = dma_resv_lock(obj->base.resv, ww ? &ww->ctx : NULL);
> + ret = dma_resv_lock(obj->base.resv, ww ? ww->ctx : NULL);
>
> if (!ret && ww) {
> i915_gem_object_get(obj);
> @@ -216,7 +216,7 @@ static inline bool i915_gem_object_trylock(struct drm_i915_gem_object *obj,
> if (!ww)
> return dma_resv_trylock(obj->base.resv);
> else
> - return ww_mutex_trylock(&obj->base.resv->lock, &ww->ctx);
> + return ww_mutex_trylock(&obj->base.resv->lock, ww->ctx);
> }
>
> static inline void i915_gem_object_unlock(struct drm_i915_gem_object *obj)
> diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
> index f025ee4fa526..047f72e32d47 100644
> --- a/drivers/gpu/drm/i915/i915_gem_evict.c
> +++ b/drivers/gpu/drm/i915/i915_gem_evict.c
> @@ -458,7 +458,7 @@ int i915_gem_evict_vm(struct i915_address_space *vm, struct i915_gem_ww_ctx *ww)
> * need the object ref.
> */
> if (dying_vma(vma) ||
> - (ww && (dma_resv_locking_ctx(vma->obj->base.resv) == &ww->ctx))) {
> + (ww && (dma_resv_locking_ctx(vma->obj->base.resv) == ww->ctx))) {
> __i915_vma_pin(vma);
> list_add(&vma->evict_link, &locked_eviction_list);
> continue;
> diff --git a/drivers/gpu/drm/i915/i915_gem_ww.c b/drivers/gpu/drm/i915/i915_gem_ww.c
> index 3f6ff139478e..c47898993c7d 100644
> --- a/drivers/gpu/drm/i915/i915_gem_ww.c
> +++ b/drivers/gpu/drm/i915/i915_gem_ww.c
> @@ -6,12 +6,20 @@
> #include "i915_gem_ww.h"
> #include "gem/i915_gem_object.h"
>
> -void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ww, bool intr)
> +void i915_gem_ww_ctx_prep(struct i915_gem_ww_ctx *ww,
> + struct ww_acquire_ctx *ww_ctx,
> + bool intr)
> {
> - ww_acquire_init(&ww->ctx, &reservation_ww_class);
> INIT_LIST_HEAD(&ww->obj_list);
> ww->intr = intr;
> ww->contended = NULL;
> + ww->ctx = ww_ctx;
> +}
> +
> +void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ww, bool intr)
> +{
> + ww_acquire_init(&ww->ww_ctx, &reservation_ww_class);
> + i915_gem_ww_ctx_prep(ww, &ww->ww_ctx, intr);
> }
>
> static void i915_gem_ww_ctx_unlock_all(struct i915_gem_ww_ctx *ww)
> @@ -36,7 +44,15 @@ void i915_gem_ww_ctx_fini(struct i915_gem_ww_ctx *ww)
> {
> i915_gem_ww_ctx_unlock_all(ww);
> WARN_ON(ww->contended);
> - ww_acquire_fini(&ww->ctx);
> +
> + if (ww->ctx == &ww->ww_ctx)
> + ww_acquire_fini(ww->ctx);
> +}
> +
> +void i915_gem_ww_ctx_fini2(struct i915_gem_ww_ctx *ww)
> +{
> + i915_gem_ww_ctx_unlock_all(ww);
> + WARN_ON(ww->contended);
> }
>
> int __must_check i915_gem_ww_ctx_backoff(struct i915_gem_ww_ctx *ww)
> @@ -48,9 +64,9 @@ int __must_check i915_gem_ww_ctx_backoff(struct i915_gem_ww_ctx *ww)
>
> i915_gem_ww_ctx_unlock_all(ww);
> if (ww->intr)
> - ret = dma_resv_lock_slow_interruptible(ww->contended->base.resv, &ww->ctx);
> + ret = dma_resv_lock_slow_interruptible(ww->contended->base.resv, ww->ctx);
> else
> - dma_resv_lock_slow(ww->contended->base.resv, &ww->ctx);
> + dma_resv_lock_slow(ww->contended->base.resv, ww->ctx);
>
> if (!ret)
> list_add_tail(&ww->contended->obj_link, &ww->obj_list);
> diff --git a/drivers/gpu/drm/i915/i915_gem_ww.h b/drivers/gpu/drm/i915/i915_gem_ww.h
> index 86f0fe343de6..e9b0fd4debbf 100644
> --- a/drivers/gpu/drm/i915/i915_gem_ww.h
> +++ b/drivers/gpu/drm/i915/i915_gem_ww.h
> @@ -8,13 +8,17 @@
> #include <drm/drm_drv.h>
>
> struct i915_gem_ww_ctx {
> - struct ww_acquire_ctx ctx;
> + struct ww_acquire_ctx *ctx;
> + struct ww_acquire_ctx ww_ctx;
> struct list_head obj_list;
> struct drm_i915_gem_object *contended;
> bool intr;
> };
>
> -void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
> +void i915_gem_ww_ctx_prep(struct i915_gem_ww_ctx *ww,
> + struct ww_acquire_ctx *ww_ctx,
> + bool intr);
> +void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ww, bool intr);
> void i915_gem_ww_ctx_fini(struct i915_gem_ww_ctx *ctx);
> int __must_check i915_gem_ww_ctx_backoff(struct i915_gem_ww_ctx *ctx);
> void i915_gem_ww_unlock_single(struct drm_i915_gem_object *obj);
> @@ -38,4 +42,11 @@ static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err)
> for (i915_gem_ww_ctx_init(_ww, _intr), (_err) = -EDEADLK; \
> (_err) == -EDEADLK; \
> (_err) = __i915_gem_ww_fini(_ww, _err))
> +
> +#define for_i915_dmabuf_ww(_ww, _dmabuf, _err, _intr) \
> + for (i915_gem_ww_ctx_prep(_ww, dma_resv_locking_ctx((_dmabuf)->resv), _intr), \
> + (_err) = -EDEADLK; \
> + (_err) == -EDEADLK; \
> + (_err) = __i915_gem_ww_fini(_ww, _err))
> +
> #endif
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