[PATCH] drm/amd/amdgpu: fix missing lock for cper.ring->rptr/wptr access

[Yang Wang]

Add lock protection for 'ring->wptr'/'ring->rptr' to ensure the correct 
execution.

Fixes: 8652920d2c00 ("drm/amdgpu: add mutex lock for cper ring")
Signed-off-by: Yang Wang <kevinyang.w...@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cper.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cper.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_cper.c
index 15dde1f50328..25252231a68a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cper.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cper.c
@@ -459,7 +459,7 @@ static u32 amdgpu_cper_ring_get_ent_sz(struct amdgpu_ring 
*ring, u64 pos)
 
 void amdgpu_cper_ring_write(struct amdgpu_ring *ring, void *src, int count)
 {
-       u64 pos, wptr_old, rptr = *ring->rptr_cpu_addr & ring->ptr_mask;
+       u64 pos, wptr_old, rptr;
        int rec_cnt_dw = count >> 2;
        u32 chunk, ent_sz;
        u8 *s = (u8 *)src;
@@ -472,9 +472,11 @@ void amdgpu_cper_ring_write(struct amdgpu_ring *ring, void 
*src, int count)
                return;
        }
 
+       mutex_lock(&ring->adev->cper.ring_lock);
+
        wptr_old = ring->wptr;
+       rptr = *ring->rptr_cpu_addr & ring->ptr_mask;
 
-       mutex_lock(&ring->adev->cper.ring_lock);
        while (count) {
                ent_sz = amdgpu_cper_ring_get_ent_sz(ring, ring->wptr);
                chunk = umin(ent_sz, count);
-- 
2.34.1