[PATCH] drm/rockchip: cancel pending vblanks on close

John Keeping
2016-03-11T17:21:53Z

When closing the DRM device while a vblank is pending, we access
file_priv after it has been free'd, which gives:

Unable to handle kernel NULL pointer dereference at virtual address 00000000
...
PC is at __list_add+0x5c/0xe8
LR is at send_vblank_event+0x54/0x1f0
...
[<c02952e8>] (__list_add) from [<c031a7b4>] (send_vblank_event+0x54/0x1f0)
[<c031a760>] (send_vblank_event) from [<c031a9c0>] (drm_send_vblank_event+0x70/0x78)
[<c031a950>] (drm_send_vblank_event) from [<c031a9f8>] (drm_crtc_send_vblank_event+0x30/0x34)
[<c031a9c8>] (drm_crtc_send_vblank_event) from [<c0339ad8>] (vop_isr+0x224/0x28c)
[<c03398b4>] (vop_isr) from [<c0081780>] (handle_irq_event_percpu+0x12c/0x3e4)

This can be triggered somewhat reliably with:

modetest -M rockchip -v -s ...

Add a preclose hook to the driver so that we can discard any pending
vblank events when the device is closed.

Signed-off-by: John Keeping <john@metanate.com>
---
drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 22 ++++++++++++++++++++++
drivers/gpu/drm/rockchip/rockchip_drm_drv.h | 1 +
drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 20 ++++++++++++++++++++
3 files changed, 43 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index a0d51cc..1c8a9be 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -251,6 +251,27 @@ static int rockchip_drm_unload(struct drm_device *drm_dev)
return 0;
}

+static void rockchip_drm_crtc_cancel_pending_vblank(struct drm_crtc *crtc,
+ struct drm_file *file_priv)
+{
+ struct rockchip_drm_private *priv = crtc->dev->dev_private;
+ int pipe = drm_crtc_index(crtc);
+
+ if (pipe < ROCKCHIP_MAX_CRTC &&
+ priv->crtc_funcs[pipe] &&
+ priv->crtc_funcs[pipe]->cancel_pending_vblank)
+ priv->crtc_funcs[pipe]->cancel_pending_vblank(crtc, file_priv);
+}
+
+static void rockchip_drm_preclose(struct drm_device *dev,
+ struct drm_file *file_priv)
+{
+ struct drm_crtc *crtc;
+
+ list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
+ rockchip_drm_crtc_cancel_pending_vblank(crtc, file_priv);
+}
+
void rockchip_drm_lastclose(struct drm_device *dev)
{
struct rockchip_drm_private *priv = dev->dev_private;
@@ -281,6 +302,7 @@ static struct drm_driver rockchip_drm_driver = {
DRIVER_PRIME | DRIVER_ATOMIC,
.load = rockchip_drm_load,
.unload = rockchip_drm_unload,
+ .preclose = rockchip_drm_preclose,
.lastclose = rockchip_drm_lastclose,
.get_vblank_counter = drm_vblank_no_hw_counter,
.enable_vblank = rockchip_drm_crtc_enable_vblank,
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
index bb8b076..2b41dd4 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
@@ -40,6 +40,7 @@ struct rockchip_crtc_funcs {
int (*enable_vblank)(struct drm_crtc *crtc);
void (*disable_vblank)(struct drm_crtc *crtc);
void (*wait_for_update)(struct drm_crtc *crtc);
+ void (*cancel_pending_vblank)(struct drm_crtc *crtc, struct drm_file *file_priv);
};

struct rockchip_atomic_commit {
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
index 8a5ac57..53dfe21 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
@@ -875,10 +875,30 @@ static void vop_crtc_wait_for_update(struct drm_crtc *crtc)
WARN_ON(!wait_for_completion_timeout(&vop->wait_update_complete, 100));
}

+static void vop_crtc_cancel_pending_vblank(struct drm_crtc *crtc,
+ struct drm_file *file_priv)
+{
+ struct drm_device *drm = crtc->dev;
+ struct vop *vop = to_vop(crtc);
+ struct drm_pending_vblank_event *e;
+ unsigned long flags;
+
+ spin_lock_irqsave(&drm->event_lock, flags);
+ e = vop->event;
+ if (e && e->base.file_priv == file_priv) {
+ vop->event = NULL;
+
+ e->base.destroy(&e->base);
+ file_priv->event_space += sizeof(e->event);
+ }
+ spin_unlock_irqrestore(&drm->event_lock, flags);
+}
+
static const struct rockchip_crtc_funcs private_crtc_funcs = {
.enable_vblank = vop_crtc_enable_vblank,
.disable_vblank = vop_crtc_disable_vblank,
.wait_for_update = vop_crtc_wait_for_update,
+ .cancel_pending_vblank = vop_crtc_cancel_pending_vblank,
};

static bool vop_crtc_mode_fixup(struct drm_crtc *crtc,
--
2.7.0.226.gfe986fe