[PATCH AUTOSEL 4.18 106/136] drm/v3d: Take a lock across GPU scheduler job creation and queuing.

[Sasha Levin]

From: Eric Anholt <e...@anholt.net>

[ Upstream commit 7122b68b8a9692dcc3acf89595f04c492872115f ]

Between creation and queueing of a job, you need to prevent any other
job from being created and queued.  Otherwise the scheduler's fences
may be signaled out of seqno order.

v2: move mutex unlock to the error label.

Signed-off-by: Eric Anholt <e...@anholt.net>
Fixes: 57692c94dcbe ("drm/v3d: Introduce a new DRM driver for Broadcom V3D 
V3.x+")
Link: 
https://patchwork.freedesktop.org/patch/msgid/20180606174851.12433-1-e...@anholt.net
Reviewed-by: Lucas Stach <l.st...@pengutronix.de>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 drivers/gpu/drm/v3d/v3d_drv.h | 5 +++++
 drivers/gpu/drm/v3d/v3d_gem.c | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/v3d/v3d_drv.h b/drivers/gpu/drm/v3d/v3d_drv.h
index a043ac3aae98..26005abd9c5d 100644
--- a/drivers/gpu/drm/v3d/v3d_drv.h
+++ b/drivers/gpu/drm/v3d/v3d_drv.h
@@ -85,6 +85,11 @@ struct v3d_dev {
         */
        struct mutex reset_lock;
 
+       /* Lock taken when creating and pushing the GPU scheduler
+        * jobs, to keep the sched-fence seqnos in order.
+        */
+       struct mutex sched_lock;
+
        struct {
                u32 num_allocated;
                u32 pages_allocated;
diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
index b513f9189caf..269fe16379c0 100644
--- a/drivers/gpu/drm/v3d/v3d_gem.c
+++ b/drivers/gpu/drm/v3d/v3d_gem.c
@@ -550,6 +550,7 @@ v3d_submit_cl_ioctl(struct drm_device *dev, void *data,
        if (ret)
                goto fail;
 
+       mutex_lock(&v3d->sched_lock);
        if (exec->bin.start != exec->bin.end) {
                ret = drm_sched_job_init(&exec->bin.base,
                                         &v3d->queue[V3D_BIN].sched,
@@ -576,6 +577,7 @@ v3d_submit_cl_ioctl(struct drm_device *dev, void *data,
        kref_get(&exec->refcount); /* put by scheduler job completion */
        drm_sched_entity_push_job(&exec->render.base,
                                  &v3d_priv->sched_entity[V3D_RENDER]);
+       mutex_unlock(&v3d->sched_lock);
 
        v3d_attach_object_fences(exec);
 
@@ -594,6 +596,7 @@ v3d_submit_cl_ioctl(struct drm_device *dev, void *data,
        return 0;
 
 fail_unreserve:
+       mutex_unlock(&v3d->sched_lock);
        v3d_unlock_bo_reservations(dev, exec, &acquire_ctx);
 fail:
        v3d_exec_put(exec);
@@ -615,6 +618,7 @@ v3d_gem_init(struct drm_device *dev)
        spin_lock_init(&v3d->job_lock);
        mutex_init(&v3d->bo_lock);
        mutex_init(&v3d->reset_lock);
+       mutex_init(&v3d->sched_lock);
 
        /* Note: We don't allocate address 0.  Various bits of HW
         * treat 0 as special, such as the occlusion query counters
-- 
2.17.1