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From 149a30121e2a4169b331e317d8061f8e523f7afa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
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 <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
---
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
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