[3.16.y-ckt stable] Patch "drm/vmwgfx: Don't use memory accounting for kernel-side fence objects" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    drm/vmwgfx: Don't use memory accounting for kernel-side fence objects

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 113f22aa64140b20774f427d31c8e649f3910829 Mon Sep 17 00:00:00 2001
From: Thomas Hellstrom <thellstrom at vmware.com>
Date: Tue, 2 Dec 2014 03:32:24 -0800
Subject: drm/vmwgfx: Don't use memory accounting for kernel-side fence objects

commit 1f563a6a46544602183e7493b6ef69769d3d76d9 upstream.

Kernel side fence objects are used when unbinding resources and may thus be
created as part of a memory reclaim operation. This might trigger recursive
memory reclaims and result in the kernel running out of stack space.

So a simple way out is to avoid accounting of these fence objects.
In principle this is OK since while user-space can trigger the creation of
such objects, it can't really hold on to them. However, their lifetime is
quite long, so some form of accounting should perhaps be implemented in the
future.

Fixes kernel crashes when running, for example viewperf11 ensight-04 test 3
with low system memory settings.

Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob at vmware.com>
Reviewed-by: Sinclair Yeh <syeh at vmware.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_fence.c | 21 ++-------------------
 1 file changed, 2 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
index b65272d7ea56..64e4fe4dd1ec 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
@@ -485,14 +485,7 @@ void vmw_fence_obj_flush(struct vmw_fence_obj *fence)

 static void vmw_fence_destroy(struct vmw_fence_obj *fence)
 {
-	struct vmw_fence_manager *fman = fence->fman;
-
 	kfree(fence);
-	/*
-	 * Free kernel space accounting.
-	 */
-	ttm_mem_global_free(vmw_mem_glob(fman->dev_priv),
-			    fman->fence_size);
 }

 int vmw_fence_create(struct vmw_fence_manager *fman,
@@ -500,20 +493,12 @@ int vmw_fence_create(struct vmw_fence_manager *fman,
 		     uint32_t mask,
 		     struct vmw_fence_obj **p_fence)
 {
-	struct ttm_mem_global *mem_glob = vmw_mem_glob(fman->dev_priv);
 	struct vmw_fence_obj *fence;
 	int ret;

-	ret = ttm_mem_global_alloc(mem_glob, fman->fence_size,
-				   false, false);
-	if (unlikely(ret != 0))
-		return ret;
-
 	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
-	if (unlikely(fence == NULL)) {
-		ret = -ENOMEM;
-		goto out_no_object;
-	}
+	if (unlikely(fence == NULL))
+		return -ENOMEM;

 	ret = vmw_fence_obj_init(fman, fence, seqno, mask,
 				 vmw_fence_destroy);
@@ -525,8 +510,6 @@ int vmw_fence_create(struct vmw_fence_manager *fman,

 out_err_init:
 	kfree(fence);
-out_no_object:
-	ttm_mem_global_free(mem_glob, fman->fence_size);
 	return ret;
 }

--
2.1.4