Am 11.04.2017 um 04:58 schrieb Huang Rui:
This patch fixes the case when buffer funcs is empty and bo evict is
executing. It must double check buffer funcs, otherwise, a NULL
pointer dereference kernel panic will be encountered.

  BUG: unable to handle kernel NULL pointer dereference at 00000000000001a4
  IP: [<ffffffffa067b6cd>] amdgpu_evict_flags+0x3d/0xf0 [amdgpu]
  PGD 0

  Oops: 0000 [#1] SMP
  Modules linked in: amdgpu(OE) ttm drm_kms_helper drm i2c_algo_bit fb_sys_fops 
syscopyarea sysfillrect sysimgblt fmem(OE) physmem_drv(OE) rpcsec_gss_krb5 
nfsv4 nfs fscache intel_rapl x86_pkg_temp_thermal intel_powerclamp 
snd_hda_codec_realtek snd_hda_codec_hdmi snd_hda_codec_generic kvm_intel 
snd_hda_intel snd_hda_codec kvm snd_hda_core joydev eeepc_wmi asus_wmi 
sparse_keymap snd_hwdep snd_pcm irqbypass crct10dif_pclmul snd_seq_midi 
snd_seq_midi_event snd_rawmidi snd_seq crc32_pclmul snd_seq_device 
ghash_clmulni_intel aesni_intel aes_x86_64 snd_timer lrw gf128mul mei_me snd 
glue_helper ablk_helper cryptd tpm_infineon mei lpc_ich serio_raw soundcore 
shpchp mac_hid nfsd auth_rpcgss nfs_acl lockd grace coretemp sunrpc parport_pc 
ppdev lp parport autofs4 hid_generic mxm_wmi r8169 usbhid ahci
   psmouse libahci nvme mii hid nvme_core wmi video
  CPU: 3 PID: 1627 Comm: kworker/u8:17 Tainted: G           OE   4.9.0-custom #1
  Hardware name: ASUS All Series/Z87-A, BIOS 1802 01/28/2014
  Workqueue: events_unbound async_run_entry_fn
  task: ffff88021e7057c0 task.stack: ffffc9000262c000
  RIP: 0010:[<ffffffffa067b6cd>]  [<ffffffffa067b6cd>] 
amdgpu_evict_flags+0x3d/0xf0 [amdgpu]
  RSP: 0018:ffffc9000262fb30  EFLAGS: 00010246
  RAX: 0000000000000000 RBX: ffff88021e8a5858 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffffc9000262fb58 RDI: ffff88021e8a5800
  RBP: ffffc9000262fb48 R08: 0000000000000000 R09: ffff88021e8a5814
  R10: 000000001def8f01 R11: ffff88021def8c80 R12: ffffc9000262fb58
  R13: ffff88021d2b1990 R14: 0000000000000000 R15: ffff88021e8a5858
  FS:  0000000000000000(0000) GS:ffff88022ed80000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00000000000001a4 CR3: 0000000001c07000 CR4: 00000000001406e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Can we have the full stack trace please?

Eviction should never occur before the buffer funcs are initialized, so that patch just papers over some kind of race condition on startup as far as I can see.

Christian.


Signed-off-by: Huang Rui <[email protected]>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index e00f66a..bbbdf50 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -221,7 +221,9 @@ static void amdgpu_evict_flags(struct ttm_buffer_object *bo,
        switch (bo->mem.mem_type) {
        case TTM_PL_VRAM:
        case AMDGPU_PL_DGMA:
-               if (adev->mman.buffer_funcs_ring->ready == false) {
+               if (adev->mman.buffer_funcs &&
+                       adev->mman.buffer_funcs_ring &&
+                       adev->mman.buffer_funcs_ring->ready == false) {
                        amdgpu_ttm_placement_from_domain(abo, 
AMDGPU_GEM_DOMAIN_CPU);
                } else {
                        amdgpu_ttm_placement_from_domain(abo, 
AMDGPU_GEM_DOMAIN_GTT);


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