From 149a30121e2a4169b331e317d8061f8e523f7afa Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Christian=20K=C3=B6nig?= Date: Fri, 11 Mar 2016 17:49:58 +0100 Subject: [PATCH 0394/1110] drm/amdgpu: cleanup amdgpu_fence_activity MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Chunming Zhou --- drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 35 +++---------------------------- 1 file changed, 3 insertions(+), 32 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c index 3db18f4..35fbc88 100644 --- 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) -- 2.7.4