[control, scheduler] Reduced scheduler lock scope.

src/video_core/control/scheduler.cpp

@@ -17,11 +17,16 @@ Scheduler::Scheduler(GPU& gpu_) : gpu{gpu_} {}
 Scheduler::~Scheduler() = default;
 
 void Scheduler::Push(s32 channel, CommandList&& entries) {
-    std::unique_lock lk(scheduling_guard);
-    auto it = channels.find(channel);
-    ASSERT(it != channels.end());
-    auto& channel_state = it->second;
-    gpu.BindChannel(channel_state->bind_id);
+    std::shared_ptr<ChannelState> channel_state;
+    {
+        std::unique_lock lk(scheduling_guard);
+        auto it = channels.find(channel);
+        ASSERT(it != channels.end());
+        channel_state = it->second;
+        gpu.BindChannel(channel_state->bind_id);
+    }
+    // Process commands outside the lock to reduce contention.
+    // Multiple channels can prepare their commands in parallel.
     channel_state->dma_pusher->Push(std::move(entries));
     channel_state->dma_pusher->DispatchCalls();
 }