2012/12/5 Inki Dae <inki.dae@xxxxxxxxxxx>
I have tested modetest 10 times and below is the result,
Before modetest is tested:
MemTotal: 1025260 kB
MemFree: 977584 kB
Buffers: 7740 kB
Cached: 5780 kB
After modetest is tested 10 times(modetest -v -s 17@4:1280x720):
MemTotal: 1025260 kB
MemFree: 979652 kB
Buffers: 7748 kB
Cached: 5908 kB
Thus, we can't find any memory leak. So I think you missed something.
2012/12/4 Prathyush K <prathyush@xxxxxxxxxxxx>On Tue, Dec 4, 2012 at 5:44 PM, Inki Dae <inki.dae@xxxxxxxxxxx> wrote:
Changelog v2:
fix page fault issue.
- defer to unreference old fb to avoid page fault issue.
So with this fixup, new fb would be updated to hardware
prior to old fb unreferencing. And it removes unnecessary
patch, "drm/exynos: Unreference fb in exynos_disable_plane()"
Changelog v1:
This patch releases the fb pended by page flip after fbdev isdrivers/gpu/drm/exynos/exynos_drm_plane.c | 28 ++++++++++++++++++-
restored propely. And fixes invalid memory access when drm is
released while doing pageflip.
This patch makes fb's refcount to be increased when setcrtc and
pageflip are requested. In other words, it increases fb's refcount
only if dma is going to access memory region to fb and decreases
old fb's because the old fb isn't accessed by dma anymore.
This could guarantee releasing gem buffer to the fb after dma
access to the gem buffer has been completed.
Signed-off-by: Inki Dae <inki.dae@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
---
drivers/gpu/drm/exynos/exynos_drm_crtc.c | 42 ++++++++++++++++++++++++++++-
drivers/gpu/drm/exynos/exynos_drm_fb.c | 23 ++++++++++++++++
drivers/gpu/drm/exynos/exynos_drm_fb.h | 6 ++++
drivers/gpu/drm/exynos/exynos_drm_fbdev.c | 9 ++++++
5 files changed, 106 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/exynos/exynos_drm_crtc.c b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
index 2efa4b0..b9c37eb 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_crtc.c@@ -139,8 +140,25 @@ exynos_drm_crtc_mode_set(struct drm_crtc *crtc, struct drm_display_mode *mode,
+++ b/drivers/gpu/drm/exynos/exynos_drm_crtc.c
@@ -32,6 +32,7 @@
#include "exynos_drm_drv.h"
#include "exynos_drm_encoder.h"
#include "exynos_drm_plane.h"
+#include "exynos_drm_fb.h"
#define to_exynos_crtc(x) container_of(x, struct exynos_drm_crtc,\
drm_crtc)
plane->crtc = crtc;
plane->fb = crtc->fb;
+ /*
+ * Take a reference to new fb.
+ *
+ * Taking a reference means that this plane's dma is going to access
+ * memory region to the new fb.
+ */
+ drm_framebuffer_reference(plane->fb);
+Hi Mr. Dae,There is an issue with this approach.Take this simple use case with just one crtc. (fbdev = fb0)First, set fb1we reference fb1 and unreference fb0.Second, remove fb1In this case, we are removing the current fb of the crtcWe hit the function 'drm_helper_disable_unused_functions'.Here, we try to disable the crtc and then we set crtc->fb = NULL.So the value of crtc->fb is lost.
After drm release, we restore fbdev mode.Now we reference fb0 - but we fail to unreference fb1. (old_fb is NULL)So fb1 never gets freed thus causing a memory leak.No, please see drm_framebuffer_remove funtion. At this function, drm_framebuffer_unreference(fb1) is called so the fb1 is released correctly after the crtc to current fb1 is disabled like below,drm_framebuffer_remove(...){disable the crtc to current fb1disable all planes to current fb1...drm_framebuffer_unreference(fb1); <- here}So unreferencing to fb1 is igonored because of NULL at fbdev restore.I tested this with modetest and each time the fb/gem memory never gets freed.Really? is there any case that drm_framebuffer_unreference(fb1) isn't called. I couldn't find any memory leak. Anyway, I will check it again.
I have tested modetest 10 times and below is the result,
Before modetest is tested:
MemTotal: 1025260 kB
MemFree: 977584 kB
Buffers: 7740 kB
Cached: 5780 kB
After modetest is tested 10 times(modetest -v -s 17@4:1280x720):
MemTotal: 1025260 kB
MemFree: 979652 kB
Buffers: 7748 kB
Cached: 5908 kB
Thus, we can't find any memory leak. So I think you missed something.
Also, another issue:If a page flip is pending, you set the 'pending' flag and do not actually unreference the fb.And you are freeing that fb after fbdev is restored.Ok, I had mentioned about this before but leave it below again and also refer to the below email threads,crtc0's current fb is fb0page flip request(crtc0, fb1)1. drm_vblank_get call2. vsync occurs and the dma access memory region to fb0 yet.3. crtc0->fb = fb14. drm is released5. crtc's current fb is fb1 but the dma is accessing memory region to fb0 yet because vsync doesn't occur so fb0 doesn't disable crtc and releses its own gem buffer. At this time, page fault would be induced because dma is still accessing the fb0 but the fb0 had already been released.So this patch defers fb releasing until fbdev is restored by drm release to avoid the page fault issue.In a normal setup, we release DRM only during system shutdown i.e. we open the drmdevice during boot up and do not release drm till the end. But we keep page flipping and removingframebuffers all the time.In this case, the pending fb memory does not get freed till we actually release drm at thevery end.For this, I mentioned above.(to defer fb releasing)I am not sure why this approach is required.We are anyway waiting for vblank before removing a framebuffer so we can be sure thatthe dma has stopped accessing the fb. Right?No, the fb to be released could be different from current fb like below,dma is accessing fb0current fb is fb1try to release fb0 so crtc isn't disabled because the fb0 is not current fb and then the fb0 is released. (page fault!!!)Thanks,Inki DaeRegards,Prathyushexynos_drm_fn_encoder(crtc, &pipe, exynos_drm_encoder_crtc_pipe);return 0;
+ /*
+ * If old_fb exists, unreference the fb.
+ *
+ * This means that memory region to the fb isn't accessed by the dma
+ * of this plane anymore.
+ */
+ if (old_fb)
+ drm_framebuffer_unreference(old_fb);
+
}
@@ -169,8 +187,27 @@ static int exynos_drm_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
if (ret)
return ret;
+ plane->fb = crtc->fb;+
+
+ /*
+ * Take a reference to new fb.
+ *
+ * Taking a reference means that this plane's dma is going to access
+ * memory region to the new fb.
+ */
+ drm_framebuffer_reference(plane->fb);
exynos_drm_crtc_commit(crtc);
return 0;
+ /*
+ * If old_fb exists, unreference the fb.
+ *
+ * This means that memory region to the fb isn't accessed by the dma
+ * of this plane anymore.
+ */
+ if (old_fb)
+ drm_framebuffer_unreference(old_fb);
+
}index 7190b64..7ed5507 100644
@@ -243,7 +280,7 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
crtc->fb = fb;
ret = exynos_drm_crtc_mode_set_base(crtc, crtc->x, crtc->y,
- NULL);
+ old_fb);
if (ret) {
crtc->fb = old_fb;
@@ -254,6 +291,9 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
goto out;
}
+
+ exynos_drm_fb_set_pending(old_fb, false);
+ exynos_drm_fb_set_pending(fb, true);
}
out:
mutex_unlock(&dev->struct_mutex);
diff --git a/drivers/gpu/drm/exynos/exynos_drm_fb.c b/drivers/gpu/drm/exynos/exynos_drm_fb.c
--- a/drivers/gpu/drm/exynos/exynos_drm_fb.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fb.c
@@ -45,11 +45,15 @@
* @fb: drm framebuffer obejct.static int check_fb_gem_memory_type(struct drm_device *drm_dev,
* @buf_cnt: a buffer count to drm framebuffer.
* @exynos_gem_obj: array of exynos specific gem object containing a gem object.
+ * @pending: indicate whehter a fb was pended by page flip.
+ * if true, the fb should be released after fbdev is restored to avoid
+ * accessing invalid memory region.
*/
struct exynos_drm_fb {
struct drm_framebuffer fb;
unsigned int buf_cnt;
struct exynos_drm_gem_obj *exynos_gem_obj[MAX_FB_BUFFER];
+ bool pending;
};
@@ -278,6 +282,25 @@ exynos_user_fb_create(struct drm_device *dev, struct drm_file *file_priv,
index 862ca1e..81d7323 100644return fb;
}
+void exynos_drm_fb_set_pending(struct drm_framebuffer *fb, bool pending)
+{
+ struct exynos_drm_fb *exynos_fb;
+
+ exynos_fb = to_exynos_fb(fb);
+
+ exynos_fb->pending = pending;
+}
+
+void exynos_drm_release_pended_fb(struct drm_framebuffer *fb)
+{
+ struct exynos_drm_fb *exynos_fb;
+
+ exynos_fb = to_exynos_fb(fb);
+
+ if (exynos_fb->pending)
+ drm_framebuffer_unreference(fb);
+}
+
struct exynos_drm_gem_buf *exynos_drm_fb_buffer(struct drm_framebuffer *fb,
int index)
{
diff --git a/drivers/gpu/drm/exynos/exynos_drm_fb.h b/drivers/gpu/drm/exynos/exynos_drm_fb.h
index 96262e5..6b63bb1 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fb.h
+++ b/drivers/gpu/drm/exynos/exynos_drm_fb.h
@@ -33,6 +33,12 @@ exynos_drm_framebuffer_init(struct drm_device *dev,
struct drm_mode_fb_cmd2 *mode_cmd,
struct drm_gem_object *obj);
+/* set fb->pending variable to desired value. */
+void exynos_drm_fb_set_pending(struct drm_framebuffer *fb, bool pending);
+
+/* release a fb pended by page flip. */
+void exynos_drm_release_pended_fb(struct drm_framebuffer *fb);
+
/* get memory information of a drm framebuffer */
struct exynos_drm_gem_buf *exynos_drm_fb_buffer(struct drm_framebuffer *fb,
int index);
diff --git a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
index e7466c4..62f3b9e 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
@@ -314,9 +314,18 @@ void exynos_drm_fbdev_fini(struct drm_device *dev)
void exynos_drm_fbdev_restore_mode(struct drm_device *dev)
{
struct exynos_drm_private *private = dev->dev_private;
+ struct drm_framebuffer *fb, *fbt;
if (!private || !private->fb_helper)
return;
drm_fb_helper_restore_fbdev_mode(private->fb_helper);
+
+ mutex_lock(&dev->mode_config.mutex);
+
+ /* Release fb pended by page flip. */
+ list_for_each_entry_safe(fb, fbt, &dev->mode_config.fb_list, head)
+ exynos_drm_release_pended_fb(fb);
+
+ mutex_unlock(&dev->mode_config.mutex);
}
diff --git a/drivers/gpu/drm/exynos/exynos_drm_plane.c b/drivers/gpu/drm/exynos/exynos_drm_plane.c
--- a/drivers/gpu/drm/exynos/exynos_drm_plane.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_plane.c
@@ -203,11 +203,29 @@ exynos_update_plane(struct drm_plane *plane, struct drm_crtc *crtc,
if (ret < 0)
return ret;
- plane->crtc = crtc;
+ /*
+ * Take a reference to new fb.+ /*
+ *
+ * Taking a reference means that this plane's dma is going to access
+ * memory region to the new fb.
+ */
+ drm_framebuffer_reference(fb);
+ plane->crtc = crtc;
exynos_plane_commit(plane);
exynos_plane_dpms(plane, DRM_MODE_DPMS_ON);
+ * If plane->fb is existed, unreference the fb.
+ *+ plane->fb = fb;
+ * This means that memory region to the fb isn't accessed by the dma
+ * of this plane anymore.
+ */
+ if (plane->fb)
+ drm_framebuffer_unreference(plane->fb);
+
+
return 0;
}
@@ -215,6 +233,14 @@ static int exynos_disable_plane(struct drm_plane *plane)
{
DRM_DEBUG_KMS("[%d] %s\n", __LINE__, __func__);
+ /*
+ * Unreference the (current)fb if plane->fb is existed.
+ * In exynos_update_plane(), the new fb reference count can be bigger
+ * than 1. So it can't be removed for that reference count.
+ */exynos_plane_dpms(plane, DRM_MODE_DPMS_OFF);
+ if (plane->fb)
+ drm_framebuffer_unreference(plane->fb);
+
return 0;
--
1.7.4.1
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