[Linux/Threading] Self-suspend with condition variable instead of spin

src/xenia/kernel/xthread.h

@@ -15,6 +15,10 @@
 #include <string>
 
 #include "xenia/base/mutex.h"
+#if XE_PLATFORM_LINUX
+#include <condition_variable>
+#include <mutex>
+#endif
 #include "xenia/base/threading.h"
 #include "xenia/cpu/thread.h"
 #include "xenia/cpu/thread_state.h"
@@ -426,6 +430,13 @@ class XThread : public XObject, public cpu::Thread {
   X_STATUS Delay(uint32_t processor_mode, uint32_t alertable,
                  uint64_t interval);
 
+#if XE_PLATFORM_LINUX
+  // Performs self-suspension: increments suspend_count and blocks until
+  // another thread calls Resume() and suspend_count reaches 0.
+  // Returns the previous suspend_count value.
+  uint32_t SelfSuspend();
+#endif
+
   xe::threading::Thread* thread() { return thread_.get(); }
 
   virtual bool Save(ByteStream* stream) override;
@@ -467,6 +478,12 @@ class XThread : public XObject, public cpu::Thread {
 
   int32_t priority_ = 0;
 
+#if XE_PLATFORM_LINUX
+  // Condition variable for thread self-suspension.
+  std::mutex suspend_mutex_;
+  std::condition_variable suspend_cv_;
+#endif
+
   // Reentry context for setjmp/longjmp based stack unwinding
   std::jmp_buf reentry_jmp_buf_;
   uint32_t reentry_address_ = 0;