[PATCH 2/3] drm/amdgpu: fix the fence timeline null pointer

[Huang Rui]

Initialize the flags for embedded fence in the job at dma_fence_init().
Otherwise, we will go a wrong way in amdgpu_fence_get_timeline_name
callback and trigger a null pointer panic once we enabled the trace event
here.

[  156.131790] BUG: kernel NULL pointer dereference, address: 00000000000002a0
[  156.131804] #PF: supervisor read access in kernel mode
[  156.131811] #PF: error_code(0x0000) - not-present page
[  156.131817] PGD 0 P4D 0
[  156.131824] Oops: 0000 [#1] PREEMPT SMP PTI
[  156.131832] CPU: 6 PID: 1404 Comm: sdma0 Tainted: G           OE     5.16.0-rc1-custom #1
[  156.131842] Hardware name: Gigabyte Technology Co., Ltd. Z170XP-SLI/Z170XP-SLI-CF, BIOS F20 11/04/2016
[  156.131848] RIP: 0010:strlen+0x0/0x20
[  156.131859] Code: 89 c0 c3 0f 1f 80 00 00 00 00 48 01 fe eb 0f 0f b6 07 38 d0 74 10 48 83 c7 01 84 c0 74 05 48 39 f7 75 ec 31 c0 c3 48 89 f8 c3 <80> 3f 00 74 10 48 89 f8 48 83 c0 01 80 38 00 75 f7 48 29 f8 c3 31
[  156.131872] RSP: 0018:ffff9bd0018dbcf8 EFLAGS: 00010206
[  156.131880] RAX: 00000000000002a0 RBX: ffff8d0305ef01b0 RCX: 000000000000000b
[  156.131888] RDX: ffff8d03772ab924 RSI: ffff8d0305ef01b0 RDI: 00000000000002a0
[  156.131895] RBP: ffff9bd0018dbd60 R08: ffff8d03002094d0 R09: 0000000000000000
[  156.131901] R10: 000000000000005e R11: 0000000000000065 R12: ffff8d03002094d0
[  156.131907] R13: 000000000000001f R14: 0000000000070018 R15: 0000000000000007
[  156.131914] FS:  0000000000000000(0000) GS:ffff8d062ed80000(0000) knlGS:0000000000000000
[  156.131923] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  156.131929] CR2: 00000000000002a0 CR3: 000000001120a005 CR4: 00000000003706e0
[  156.131937] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  156.131942] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  156.131949] Call Trace:
[  156.131953]  <TASK>
[  156.131957]  ? trace_event_raw_event_dma_fence+0xcc/0x200
[  156.131973]  ? ring_buffer_unlock_commit+0x23/0x130
[  156.131982]  dma_fence_init+0x92/0xb0
[  156.131993]  amdgpu_fence_emit+0x10d/0x2b0 [amdgpu]
[  156.132302]  amdgpu_ib_schedule+0x2f9/0x580 [amdgpu]
[  156.132586]  amdgpu_job_run+0xed/0x220 [amdgpu]

Signed-off-by: Huang Rui <ray.huang at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index 3b7e86ea7167..e2aa71904278 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -76,7 +76,7 @@ void amdgpu_fence_slab_fini(void)
 /*
  * Cast helper
  */
-static const struct dma_fence_ops amdgpu_fence_ops;
+static struct dma_fence_ops amdgpu_fence_ops;
 static inline struct amdgpu_fence *to_amdgpu_fence(struct dma_fence *f)
 {
 	struct amdgpu_fence *__f = container_of(f, struct amdgpu_fence, base);
@@ -158,21 +158,22 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f, struct amd
 	}
 
 	seq = ++ring->fence_drv.sync_seq;
-	if (job != NULL && job->job_run_counter) {
+	if (job && job->job_run_counter) {
 		/* reinit seq for resubmitted jobs */
 		fence->seqno = seq;
+		set_bit(AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT, &fence->flags);
 	} else {
+		amdgpu_fence_ops.init_flags = 0;
+		if (job)
+			set_bit(AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT,
+				&amdgpu_fence_ops.init_flags);
+
 		dma_fence_init(fence, &amdgpu_fence_ops,
 				&ring->fence_drv.lock,
 				adev->fence_context + ring->idx,
 				seq);
 	}
 
-	if (job != NULL) {
-		/* mark this fence has a parent job */
-		set_bit(AMDGPU_FENCE_FLAG_EMBED_IN_JOB_BIT, &fence->flags);
-	}
-
 	amdgpu_ring_emit_fence(ring, ring->fence_drv.gpu_addr,
 			       seq, flags | AMDGPU_FENCE_FLAG_INT);
 	pm_runtime_get_noresume(adev_to_drm(adev)->dev);
@@ -720,7 +721,7 @@ static void amdgpu_fence_release(struct dma_fence *f)
 	call_rcu(&f->rcu, amdgpu_fence_free);
 }
 
-static const struct dma_fence_ops amdgpu_fence_ops = {
+static struct dma_fence_ops amdgpu_fence_ops = {
 	.get_driver_name = amdgpu_fence_get_driver_name,
 	.get_timeline_name = amdgpu_fence_get_timeline_name,
 	.enable_signaling = amdgpu_fence_enable_signaling,
-- 
2.25.1