From 3594a3e21f1f77d46e89195f36292a2fd0f4aa83 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 24 Oct 2016 13:42:16 +0100 Subject: [PATCH] drm/i915: Remove superfluous locking around userfault_list Now that we have reduced the access to the list to either (a) under the struct_mutex whilst holding the RPM wakeref (so that concurrent writers to the list are serialised by struct_mutex) and (b) under the atomic runtime suspend (which cannot run concurrently with any other accessor due to the atomic nature of the runtime suspend) we can remove the extra locking around the list itself. Signed-off-by: Chris Wilson Reviewed-by: Joonas Lahtinen Link: http://patchwork.freedesktop.org/patch/msgid/20161024124218.18252-3-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_drv.h | 3 --- drivers/gpu/drm/i915/i915_gem.c | 33 ++++++++++++--------------------- 2 files changed, 12 insertions(+), 24 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index a53172e7790f..ba87a852c0db 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -1361,9 +1361,6 @@ struct i915_gem_mm { */ struct list_head unbound_list; - /** Protects access to the userfault_list */ - spinlock_t userfault_lock; - /** List of all objects in gtt_space, currently mmaped by userspace. * All objects within this list must also be on bound_list. */ diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 63bf51b117a9..38053434da8a 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1842,10 +1842,8 @@ int i915_gem_fault(struct vm_area_struct *area, struct vm_fault *vmf) /* Mark as being mmapped into userspace for later revocation */ assert_rpm_wakelock_held(dev_priv); - spin_lock(&dev_priv->mm.userfault_lock); if (list_empty(&obj->userfault_link)) list_add(&obj->userfault_link, &dev_priv->mm.userfault_list); - spin_unlock(&dev_priv->mm.userfault_lock); /* Finally, remap it using the new GTT offset */ ret = remap_io_mapping(area, @@ -1922,7 +1920,6 @@ void i915_gem_release_mmap(struct drm_i915_gem_object *obj) { struct drm_i915_private *i915 = to_i915(obj->base.dev); - bool zap = false; /* Serialisation between user GTT access and our code depends upon * revoking the CPU's PTE whilst the mutex is held. The next user @@ -1935,15 +1932,10 @@ i915_gem_release_mmap(struct drm_i915_gem_object *obj) lockdep_assert_held(&i915->drm.struct_mutex); intel_runtime_pm_get(i915); - spin_lock(&i915->mm.userfault_lock); - if (!list_empty(&obj->userfault_link)) { - list_del_init(&obj->userfault_link); - zap = true; - } - spin_unlock(&i915->mm.userfault_lock); - if (!zap) + if (list_empty(&obj->userfault_link)) goto out; + list_del_init(&obj->userfault_link); drm_vma_node_unmap(&obj->base.vma_node, obj->base.dev->anon_inode->i_mapping); @@ -1963,21 +1955,21 @@ out: void i915_gem_release_all_mmaps(struct drm_i915_private *dev_priv) { - struct drm_i915_gem_object *obj; + struct drm_i915_gem_object *obj, *on; - spin_lock(&dev_priv->mm.userfault_lock); - while ((obj = list_first_entry_or_null(&dev_priv->mm.userfault_list, - struct drm_i915_gem_object, - userfault_link))) { - list_del_init(&obj->userfault_link); - spin_unlock(&dev_priv->mm.userfault_lock); + /* + * Only called during RPM suspend. All users of the userfault_list + * must be holding an RPM wakeref to ensure that this can not + * run concurrently with themselves (and use the struct_mutex for + * protection between themselves). + */ + list_for_each_entry_safe(obj, on, + &dev_priv->mm.userfault_list, userfault_link) { + list_del_init(&obj->userfault_link); drm_vma_node_unmap(&obj->base.vma_node, obj->base.dev->anon_inode->i_mapping); - - spin_lock(&dev_priv->mm.userfault_lock); } - spin_unlock(&dev_priv->mm.userfault_lock); } /** @@ -4547,7 +4539,6 @@ int i915_gem_init(struct drm_device *dev) int ret; mutex_lock(&dev->struct_mutex); - spin_lock_init(&dev_priv->mm.userfault_lock); if (!i915.enable_execlists) { dev_priv->gt.resume = intel_legacy_submission_resume; -- 2.30.2