On 8/22/19 4:02 PM, Koenig, Christian wrote:
Am 22.08.19 um 15:06 schrieb Daniel Vetter:
On Thu, Aug 22, 2019 at 07:56:56AM +0000, Koenig, Christian wrote:
Am 22.08.19 um 08:49 schrieb Daniel Vetter:
With nouveau fixed all ttm-using drives have the correct nesting of
mmap_sem vs dma_resv, and we can just lock the buffer.
Assuming I didn't screw up anything with my audit of course.
v2:
- Dont forget wu_mutex (Christian König)
- Keep the mmap_sem-less wait optimization (Thomas)
- Use _lock_interruptible to be good citizens (Thomas)
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
btw I realized I didn't remove your r-b, since v1 was broken.
For formality, can you pls reaffirm, or still something broken?
My r-b is still valid.
Only problem I see is that neither of us seems to have a good idea about
the different VM_FAULT_* replies.
I took a look in mm/gup.c. It seems like when using get_user_pages,
VM_FAULT_RETRY will retry to a requesting caller telling it that a long
wait was expected and not performed, whereas VM_FAULT_NOPAGE will just
keep get_user_pages to spin. So the proposed patch should be correct
from my understanding.
If the fault originates from user-space, I guess either is fine.
/Thomas
But that worked before so it should still work now,
Christian.
Also from the other thread: Reviewed-by: Thomas Hellström <thellstrom@xxxxxxxxxx>
Thanks, Daniel
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Cc: "VMware Graphics" <linux-graphics-maintainer@xxxxxxxxxx>
Cc: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
---
drivers/gpu/drm/ttm/ttm_bo.c | 36 -------------------------------
drivers/gpu/drm/ttm/ttm_bo_util.c | 1 -
drivers/gpu/drm/ttm/ttm_bo_vm.c | 18 +++++-----------
include/drm/ttm/ttm_bo_api.h | 4 ----
4 files changed, 5 insertions(+), 54 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 20ff56f27aa4..d1ce5d315d5b 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -162,7 +162,6 @@ static void ttm_bo_release_list(struct kref *list_kref)
dma_fence_put(bo->moving);
if (!ttm_bo_uses_embedded_gem_object(bo))
dma_resv_fini(&bo->base._resv);
- mutex_destroy(&bo->wu_mutex);
bo->destroy(bo);
ttm_mem_global_free(bdev->glob->mem_glob, acc_size);
}
@@ -1319,7 +1318,6 @@ int ttm_bo_init_reserved(struct ttm_bo_device *bdev,
INIT_LIST_HEAD(&bo->ddestroy);
INIT_LIST_HEAD(&bo->swap);
INIT_LIST_HEAD(&bo->io_reserve_lru);
- mutex_init(&bo->wu_mutex);
bo->bdev = bdev;
bo->type = type;
bo->num_pages = num_pages;
@@ -1954,37 +1952,3 @@ void ttm_bo_swapout_all(struct ttm_bo_device *bdev)
;
}
EXPORT_SYMBOL(ttm_bo_swapout_all);
-
-/**
- * ttm_bo_wait_unreserved - interruptible wait for a buffer object to become
- * unreserved
- *
- * @bo: Pointer to buffer
- */
-int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo)
-{
- int ret;
-
- /*
- * In the absense of a wait_unlocked API,
- * Use the bo::wu_mutex to avoid triggering livelocks due to
- * concurrent use of this function. Note that this use of
- * bo::wu_mutex can go away if we change locking order to
- * mmap_sem -> bo::reserve.
- */
- ret = mutex_lock_interruptible(&bo->wu_mutex);
- if (unlikely(ret != 0))
- return -ERESTARTSYS;
- if (!dma_resv_is_locked(bo->base.resv))
- goto out_unlock;
- ret = dma_resv_lock_interruptible(bo->base.resv, NULL);
- if (ret == -EINTR)
- ret = -ERESTARTSYS;
- if (unlikely(ret != 0))
- goto out_unlock;
- dma_resv_unlock(bo->base.resv);
-
-out_unlock:
- mutex_unlock(&bo->wu_mutex);
- return ret;
-}
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index fe81c565e7ef..82ea26a49959 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -508,7 +508,6 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
INIT_LIST_HEAD(&fbo->base.lru);
INIT_LIST_HEAD(&fbo->base.swap);
INIT_LIST_HEAD(&fbo->base.io_reserve_lru);
- mutex_init(&fbo->base.wu_mutex);
fbo->base.moving = NULL;
drm_vma_node_reset(&fbo->base.base.vma_node);
atomic_set(&fbo->base.cpu_writers, 0);
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 76eedb963693..a61a35e57d1c 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -125,30 +125,22 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
&bdev->man[bo->mem.mem_type];
struct vm_area_struct cvma;
- /*
- * Work around locking order reversal in fault / nopfn
- * between mmap_sem and bo_reserve: Perform a trylock operation
- * for reserve, and if it fails, retry the fault after waiting
- * for the buffer to become unreserved.
- */
if (unlikely(!dma_resv_trylock(bo->base.resv))) {
if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
Not an expert on fault handling, but shouldn't this now be one if?
E.g. if FAULT_FLAG_RETRY_NOWAIT is set we should return VM_FAULT_NOPAGE
instead of VM_FAULT_RETRY.
But really take that with a grain of salt,
Christian.
ttm_bo_get(bo);
up_read(&vmf->vma->vm_mm->mmap_sem);
- (void) ttm_bo_wait_unreserved(bo);
+ if (!dma_resv_lock_interruptible(bo->base.resv,
+ NULL))
+ dma_resv_unlock(bo->base.resv);
ttm_bo_put(bo);
}
return VM_FAULT_RETRY;
}
- /*
- * If we'd want to change locking order to
- * mmap_sem -> bo::reserve, we'd use a blocking reserve here
- * instead of retrying the fault...
- */
- return VM_FAULT_NOPAGE;
+ if (dma_resv_lock_interruptible(bo->base.resv, NULL))
+ return VM_FAULT_NOPAGE;
}
/*
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 43c4929a2171..21c7d0d28757 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -155,7 +155,6 @@ struct ttm_tt;
* @offset: The current GPU offset, which can have different meanings
* depending on the memory type. For SYSTEM type memory, it should be 0.
* @cur_placement: Hint of current placement.
- * @wu_mutex: Wait unreserved mutex.
*
* Base class for TTM buffer object, that deals with data placement and CPU
* mappings. GPU mappings are really up to the driver, but for simpler GPUs
@@ -229,8 +228,6 @@ struct ttm_buffer_object {
uint64_t offset; /* GPU address space is independent of CPU word size */
struct sg_table *sg;
-
- struct mutex wu_mutex;
};
/**
@@ -765,7 +762,6 @@ ssize_t ttm_bo_io(struct ttm_bo_device *bdev, struct file *filp,
int ttm_bo_swapout(struct ttm_bo_global *glob,
struct ttm_operation_ctx *ctx);
void ttm_bo_swapout_all(struct ttm_bo_device *bdev);
-int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo);
/**
* ttm_bo_uses_embedded_gem_object - check if the given bo uses the
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