thread/Thread: add debug attribute "inside_handle"

This attribute shall be used only for IsInside() to make this safe against a race condition described in #188: > There is no requirement on the implementation that the ID of the > created thread be available before the newly created thread starts > executing. http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_create.html): This means that on some pthread implementations (e.g. Haiku), the assert(thread.IsInside()) could fail. Closes #188

thread/Thread: add debug attribute "inside_handle"
2eef4e67 · Max Kellermann · d989dbfe · 2eef4e67 · 2eef4e67 · 2eef4e67
Commit 2eef4e67 authored Jan 08, 2018 by Max Kellermann
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Showing with 16 additions and 1 deletion

NEWS NEWS +1 -0

Thread.cxx src/thread/Thread.cxx +4 -0

Thread.hxx src/thread/Thread.hxx +11 -1

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--- a/NEWS
+++ b/NEWS
 ver 0.20.16 (not yet released)
+* fix crash in debug build on Haiku and other operating systems

 ver 0.20.15 (2018/01/05)
 * queue: fix crash after seek failure

--- a/src/thread/Thread.cxx
+++ b/src/thread/Thread.cxx
@@ -86,6 +86,10 @@ Thread::ThreadProc(void *ctx)
 {
 	Thread &thread = *(Thread *)ctx;

+#ifndef NDEBUG
+	thread.inside_handle = pthread_self();
+#endif
+
 	thread.Run();

 	return nullptr;

--- a/src/thread/Thread.hxx
+++ b/src/thread/Thread.hxx
@@ -41,6 +41,16 @@ class Thread {
 	DWORD id;
 #else
 	pthread_t handle = pthread_t();
+
+#ifndef NDEBUG
+	/**
+	 * This handle is only used by IsInside(), and is set by the
+	 * thread function.  Since #handle is set by pthread_create()
+	 * which is racy, we need this attribute for early checks
+	 * inside the thread function.
+	 */
+	pthread_t inside_handle = pthread_t();
+#endif
 #endif

 public:
@@ -79,7 +89,7 @@ public:
 		   default-constructed values" (comment from
 		   libstdc++) - and if both libstdc++ and libc++ get
 		   away with this, we can do it as well */
-		return pthread_self() == handle;
+		return pthread_self() == inside_handle;
 #endif
 	}
 #endif