drm/amdgpu: cleanup amdgpu_fence_activity

The comment about the loop counter was never valid, even when you have
multiple threads this loop only runs as long as the sequence increases.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index 3db18f42c5c9883c803d9c33ff3c6c9fbae31c07..35fbc887451485dfbea428ee2c20b32e5f3478bd 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -166,30 +166,8 @@ static void amdgpu_fence_schedule_fallback(struct amdgpu_ring *ring)
 static bool amdgpu_fence_activity(struct amdgpu_ring *ring)
 {
        uint64_t seq, last_seq, last_emitted;
-       unsigned count_loop = 0;
        bool wake = false;
 
-       /* Note there is a scenario here for an infinite loop but it's
-        * very unlikely to happen. For it to happen, the current polling
-        * process need to be interrupted by another process and another
-        * process needs to update the last_seq btw the atomic read and
-        * xchg of the current process.
-        *
-        * More over for this to go in infinite loop there need to be
-        * continuously new fence signaled ie amdgpu_fence_read needs
-        * to return a different value each time for both the currently
-        * polling process and the other process that xchg the last_seq
-        * btw atomic read and xchg of the current process. And the
-        * value the other process set as last seq must be higher than
-        * the seq value we just read. Which means that current process
-        * need to be interrupted after amdgpu_fence_read and before
-        * atomic xchg.
-        *
-        * To be even more safe we count the number of time we loop and
-        * we bail after 10 loop just accepting the fact that we might
-        * have temporarly set the last_seq not to the true real last
-        * seq but to an older one.
-        */
        last_seq = atomic64_read(&ring->fence_drv.last_seq);
        do {
                last_emitted = ring->fence_drv.sync_seq;
@@ -200,23 +178,16 @@ static bool amdgpu_fence_activity(struct amdgpu_ring *ring)
                        seq |= last_emitted & 0xffffffff00000000LL;
                }
 
-               if (seq <= last_seq || seq > last_emitted) {
+               if (seq <= last_seq || seq > last_emitted)
                        break;
-               }
+
                /* If we loop over we don't want to return without
                 * checking if a fence is signaled as it means that the
                 * seq we just read is different from the previous on.
                 */
                wake = true;
                last_seq = seq;
-               if ((count_loop++) > 10) {
-                       /* We looped over too many time leave with the
-                        * fact that we might have set an older fence
-                        * seq then the current real last seq as signaled
-                        * by the hw.
-                        */
-                       break;
-               }
+
        } while (atomic64_xchg(&ring->fence_drv.last_seq, seq) > seq);
 
        if (seq < last_emitted)