From 947a1585216b0ff01bde184bccb1231626e86b57 Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Fri, 15 Jul 2022 11:20:13 +0200
Subject: [gdbsupport] Add thread_pool::id

Used to implement a poor mans thread_local.
---
 gdbsupport/thread-pool.cc | 22 +++++++++++++++++++++-
 gdbsupport/thread-pool.h  |  5 +++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/gdbsupport/thread-pool.cc b/gdbsupport/thread-pool.cc
index ddb76b69..c102aec 100644
--- a/gdbsupport/thread-pool.cc
+++ b/gdbsupport/thread-pool.cc
@@ -149,12 +149,25 @@ thread_pool::~thread_pool ()
      case -- see the comment by the definition of g_thread_pool.  */
 }
 
+unsigned thread_pool::id ()
+{
+#if CXX_STD_THREAD
+    std::thread::id id = std::this_thread::get_id();
+    return g_thread_pool->m_thread_ids[id];
+#else
+    return 0;
+#endif
+}
+
 void
 thread_pool::set_thread_count (size_t num_threads)
 {
 #if CXX_STD_THREAD
   std::lock_guard<std::mutex> guard (m_tasks_mutex);
 
+  m_thread_ids[std::this_thread::get_id ()] = 0;
+  m_thread_ids_reverse[0] = std::this_thread::get_id ();
+
   /* If the new size is larger, start some new threads.  */
   if (m_thread_count < num_threads)
     {
@@ -166,6 +179,8 @@ thread_pool::set_thread_count (size_t num_threads)
 	  try
 	    {
 	      std::thread thread (&thread_pool::thread_function, this);
+	      m_thread_ids[thread.get_id ()] = i + 1;
+	      m_thread_ids_reverse[i + 1] = thread.get_id ();
 	      thread.detach ();
 	    }
 	  catch (const std::system_error &)
@@ -182,7 +197,12 @@ thread_pool::set_thread_count (size_t num_threads)
   if (num_threads < m_thread_count)
     {
       for (size_t i = num_threads; i < m_thread_count; ++i)
-	m_tasks.emplace ();
+	{
+	  std::thread::id id = m_thread_ids_reverse[i];
+	  m_thread_ids.erase (id);
+	  m_thread_ids_reverse.erase (i);
+	  m_tasks.emplace ();
+	}
       m_tasks_cv.notify_all ();
     }
 
diff --git a/gdbsupport/thread-pool.h b/gdbsupport/thread-pool.h
index 4db35ba..788f189 100644
--- a/gdbsupport/thread-pool.h
+++ b/gdbsupport/thread-pool.h
@@ -22,6 +22,7 @@
 
 #include <queue>
 #include <vector>
+#include <unordered_map>
 #include <functional>
 #if CXX_STD_THREAD
 #include <thread>
@@ -119,6 +120,8 @@ public:
 #endif
   }
 
+  static unsigned id ();
+
   /* Post a task to the thread pool.  A future is returned, which can
      be used to wait for the result.  */
   future<void> post_task (std::function<void ()> &&func)
@@ -177,6 +180,8 @@ private:
      between the main thread and the worker threads.  */
   std::condition_variable m_tasks_cv;
   std::mutex m_tasks_mutex;
+  std::unordered_map<std::thread::id, unsigned> m_thread_ids;
+  std::unordered_map<unsigned, std::thread::id> m_thread_ids_reverse;
 #endif /* CXX_STD_THREAD */
 };
 
-- 
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