On Tue, Nov 19, 2019 at 1:08 PM 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. seems reasonable.. but maybe a comment would be useful to prevent future-me from "cleaning-this-up" back to the way it was with that, r-b > > Aside: Why is msm still using struct_mutex, it seems to be using > dma_resv_lock for general buffer state protection? only because I (or anyone else) hasn't had time to revisit the struct_mutex usage since we moved to per-object-locks.. the downside, I suppose, of kernel generally working ok and this not being a big enough fire to bubble up to the top of my todo list BR, -R > > 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 > --- > drivers/gpu/drm/msm/msm_gem_submit.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c > index fb1fdd7fa3ef..126b2f62bfe7 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; > } > @@ -489,6 +488,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data, > if (ret) > goto out; > > + ww_acquire_init(&submit->ticket, &reservation_ww_class); > ret = submit_lock_objects(submit); > if (ret) > goto out; > -- > 2.24.0 >
