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From 68dbfe7ac42974716e72e8ae3b59cdec14721d3f Mon Sep 17 00:00:00 2001
From: Xaver Hugl <xaver.hugl@gmail.com>
Date: Thu, 5 Sep 2024 16:04:16 +0200
Subject: [PATCH] backends/drm: prevent the main thread from moving the target
pageflip time forward
When the commit thread moves the target back by one refresh cycle, there's some time where
estimateNextVblank will still return the old target - so if the main thread adds another
commit to the queue and overrides the target, the commit thread's action would be undone.
---
src/backends/drm/drm_commit_thread.cpp | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
--- a/src/backends/drm/drm_commit_thread.cpp
+++ b/src/backends/drm/drm_commit_thread.cpp
@@ -23,6 +23,7 @@ namespace KWin
DrmCommitThread::DrmCommitThread(DrmGpu *gpu, const QString &name)
: m_gpu(gpu)
+ , m_targetPageflipTime(std::chrono::steady_clock::now())
{
if (!gpu->atomicModeSetting()) {
return;
@@ -313,13 +314,15 @@ void DrmCommitThread::addCommit(std::uni
std::unique_lock lock(m_mutex);
m_commits.push_back(std::move(commit));
const auto now = std::chrono::steady_clock::now();
+ TimePoint newTarget;
if (m_tearing) {
- m_targetPageflipTime = now;
+ newTarget = now;
} else if (m_vrr && now >= m_lastPageflip + m_minVblankInterval) {
- m_targetPageflipTime = now;
+ newTarget = now;
} else {
- m_targetPageflipTime = estimateNextVblank(now);
+ newTarget = estimateNextVblank(now);
}
+ m_targetPageflipTime = std::max(m_targetPageflipTime, newTarget);
m_commits.back()->setDeadline(m_targetPageflipTime - m_safetyMargin);
m_commitPending.notify_all();
}
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