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drm/i915: Only update the current userptr worker

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The userptr worker allows for a slight race condition where upon there
may two or more threads calling get_user_pages for the same object. When
we have the array of pages, then we serialise the update of the object.
However, the worker should only overwrite the obj->userptr.work pointer
if and only if it is the active one. Currently we clear it for a
secondary worker with the effect that we may rarely force a second
lookup.

v2: Rebase and rename a variable to avoid 80cols
v3: Mention v2

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Chris Wilson 2015-10-01 12:34:45 +01:00 committed by Daniel Vetter
parent 24dfd0736c
commit 68d6c84059
1 changed files with 16 additions and 16 deletions
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32
drivers/gpu/drm/i915/i915_gem_userptr.c
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@ -571,25 +571,25 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
struct get_pages_work *work = container_of(_work, typeof(*work), work);
struct drm_i915_gem_object *obj = work->obj;
struct drm_device *dev = obj->base.dev;
const int num_pages = obj->base.size >> PAGE_SHIFT;
const int npages = obj->base.size >> PAGE_SHIFT;
struct page **pvec;
int pinned, ret;
ret = -ENOMEM;
pinned = 0;
pvec = kmalloc(num_pages*sizeof(struct page *),
pvec = kmalloc(npages*sizeof(struct page *),
GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
if (pvec == NULL)
pvec = drm_malloc_ab(num_pages, sizeof(struct page *));
pvec = drm_malloc_ab(npages, sizeof(struct page *));
if (pvec != NULL) {
struct mm_struct *mm = obj->userptr.mm->mm;
down_read(&mm->mmap_sem);
while (pinned < num_pages) {
while (pinned < npages) {
ret = get_user_pages(work->task, mm,
obj->userptr.ptr + pinned * PAGE_SIZE,
num_pages - pinned,
npages - pinned,
!obj->userptr.read_only, 0,
pvec + pinned, NULL);
if (ret < 0)
@ -601,20 +601,20 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
}
mutex_lock(&dev->struct_mutex);
if (obj->userptr.work != &work->work) {
ret = 0;
} else if (pinned == num_pages) {
ret = __i915_gem_userptr_set_pages(obj, pvec, num_pages);
if (ret == 0) {
list_add_tail(&obj->global_list, &to_i915(dev)->mm.unbound_list);
obj->get_page.sg = obj->pages->sgl;
obj->get_page.last = 0;
pinned = 0;
if (obj->userptr.work == &work->work) {
if (pinned == npages) {
ret = __i915_gem_userptr_set_pages(obj, pvec, npages);
if (ret == 0) {
list_add_tail(&obj->global_list,
&to_i915(dev)->mm.unbound_list);
obj->get_page.sg = obj->pages->sgl;
obj->get_page.last = 0;
pinned = 0;
}
}
obj->userptr.work = ERR_PTR(ret);
}
obj->userptr.work = ERR_PTR(ret);
obj->userptr.workers--;
drm_gem_object_unreference(&obj->base);
mutex_unlock(&dev->struct_mutex);