On Die, 2013-05-21 at 14:23 +0800, Huacai Chen wrote:

When GPU acceleration is disabled, drm_vblank_cleanup() will free the vblank-related data, such as vblank_refcount, vblank_inmodeset, etc. But we found that drm_vblank_post_modeset() may be called after the cleanup, which use vblank_refcount and vblank_inmodeset. And this will cause a kernel panic.

Fix this by return immediately if dev->num_crtcs is zero. This is the same thing that drm_vblank_pre_modeset() does.

Call trace of a drm_vblank_post_modeset() after drm_vblank_cleanup(): [ 62.628906] [<ffffffff804868d0>] drm_vblank_post_modeset+0x34/0xb4 [ 62.628906] [<ffffffff804c7008>] atombios_crtc_dpms+0xb4/0x174 [ 62.628906] [<ffffffff804c70e0>] atombios_crtc_commit+0x18/0x38 [ 62.628906] [<ffffffff8047f038>] drm_crtc_helper_set_mode+0x304/0x3cc [ 62.628906] [<ffffffff8047f92c>] drm_crtc_helper_set_config+0x6d8/0x988 [ 62.628906] [<ffffffff8047dd40>] drm_fb_helper_set_par+0x94/0x104 [ 62.628906] [<ffffffff80439d14>] fbcon_init+0x424/0x57c [ 62.628906] [<ffffffff8046a638>] visual_init+0xb8/0x118 [ 62.628906] [<ffffffff8046b9f8>] take_over_console+0x238/0x384 [ 62.628906] [<ffffffff80436df8>] fbcon_takeover+0x7c/0xdc [ 62.628906] [<ffffffff8024fa20>] notifier_call_chain+0x44/0x94 [ 62.628906] [<ffffffff8024fcbc>] __blocking_notifier_call_chain+0x48/0x68 [ 62.628906] [<ffffffff8042d990>] register_framebuffer+0x228/0x260 [ 62.628906] [<ffffffff8047e010>] drm_fb_helper_single_fb_probe+0x260/0x314 [ 62.628906] [<ffffffff8047e2c4>] drm_fb_helper_initial_config+0x200/0x234 [ 62.628906] [<ffffffff804e5560>] radeon_fbdev_init+0xd4/0xf4 [ 62.628906] [<ffffffff804e0e08>] radeon_modeset_init+0x9bc/0xa18 [ 62.628906] [<ffffffff804bfc14>] radeon_driver_load_kms+0xdc/0x12c [ 62.628906] [<ffffffff8048b548>] drm_get_pci_dev+0x148/0x238 [ 62.628906] [<ffffffff80423564>] local_pci_probe+0x5c/0xd0 [ 62.628906] [<ffffffff80241ac4>] work_for_cpu_fn+0x1c/0x30 [ 62.628906] [<ffffffff802427c8>] process_one_work+0x274/0x3bc [ 62.628906] [<ffffffff80242934>] process_scheduled_works+0x24/0x44 [ 62.628906] [<ffffffff8024515c>] worker_thread+0x31c/0x3f4 [ 62.628906] [<ffffffff802497a8>] kthread+0x88/0x90 [ 62.628906] [<ffffffff80206794>] kernel_thread_helper+0x10/0x18

Signed-off-by: Huacai Chen chenhc@lemote.com Signed-off-by: Binbin Zhou zhoubb@lemote.com Cc: stable@vger.kernel.org

---

drivers/gpu/drm/drm_irq.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index c798eea..c7a1348 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -981,7 +981,7 @@ EXPORT_SYMBOL(drm_vblank_off); */ void drm_vblank_pre_modeset(struct drm_device *dev, int crtc) {

•   /* vblank is not initialized (IRQ not installed ?) */
  

•   /* vblank is not initialized (IRQ not installed ?), or has been freed */
    if (!dev->num_crtcs)
            return;
    /*
  

@@ -1003,6 +1003,10 @@ void drm_vblank_post_modeset(struct drm_device *dev, int crtc) { unsigned long irqflags;

•   /* vblank is not initialized (IRQ not installed ?), or has been freed */
  

•   if (!dev->num_crtcs)
  

•           return;
  

•   if (dev->vblank_inmodeset[crtc]) {
            spin_lock_irqsave(&dev->vbl_lock, irqflags);
            dev->vblank_disable_allowed = 1;
  

The comment changes seem superfluous to me, but either way:

Reviewed-by: Michel Dänzer michel.daenzer@amd.com