On Wed, Nov 20, 2019 at 2:56 AM Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > > For locking semantics it really doesn't matter when we grab the > ticket. But for lockdep validation it does: the acquire ctx is a fake > lockdep. Since other drivers might want to do a full multi-lock dance > in their fault-handler, not just lock a single dma_resv. Therefore we > must init the acquire_ctx only after we've done all the copy_*_user or > anything else that might trigger a pagefault. For msm this means we > need to move it past submit_lookup_objects. > > Aside: Why is msm still using struct_mutex, it seems to be using > dma_resv_lock for general buffer state protection? > > v2: > - Add comment to explain why the ww ticket setup is separate (Rob) > - Fix up error handling, we need to make sure we don't call > ww_acquire_fini without _init. > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > Cc: Rob Clark <robdclark@xxxxxxxxx> > Cc: Sean Paul <sean@xxxxxxxxxx> > Cc: linux-arm-msm@xxxxxxxxxxxxxxx > Cc: freedreno@xxxxxxxxxxxxxxxxxxxxx found a few minutes to take this for a spin and seems fine.. t-b && r-b BR, -R > --- > drivers/gpu/drm/msm/msm_gem_submit.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c > index fb1fdd7fa3ef..385d4965a8d0 100644 > --- a/drivers/gpu/drm/msm/msm_gem_submit.c > +++ b/drivers/gpu/drm/msm/msm_gem_submit.c > @@ -54,7 +54,6 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev, > > INIT_LIST_HEAD(&submit->node); > INIT_LIST_HEAD(&submit->bo_list); > - ww_acquire_init(&submit->ticket, &reservation_ww_class); > > return submit; > } > @@ -390,8 +389,6 @@ static void submit_cleanup(struct msm_gem_submit *submit) > list_del_init(&msm_obj->submit_entry); > drm_gem_object_put(&msm_obj->base); > } > - > - ww_acquire_fini(&submit->ticket); > } > > int msm_ioctl_gem_submit(struct drm_device *dev, void *data, > @@ -408,6 +405,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data, > struct msm_ringbuffer *ring; > int out_fence_fd = -1; > struct pid *pid = get_pid(task_pid(current)); > + bool has_ww_ticket = false; > unsigned i; > int ret, submitid; > if (!gpu) > @@ -489,6 +487,9 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data, > if (ret) > goto out; > > + /* copy_*_user while holding a ww ticket upsets lockdep */ > + ww_acquire_init(&submit->ticket, &reservation_ww_class); > + has_ww_ticket = true; > ret = submit_lock_objects(submit); > if (ret) > goto out; > @@ -588,6 +589,8 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data, > > out: > submit_cleanup(submit); > + if (has_ww_ticket) > + ww_acquire_fini(&submit->ticket); > if (ret) > msm_gem_submit_free(submit); > out_unlock: > -- > 2.24.0 >
