From 932a58ea407d6878d610cbe516d901293977aba1 Mon Sep 17 00:00:00 2001
From: Ludovic Henry <luhenry@microsoft.com>
Date: Mon, 25 Sep 2017 23:05:58 -0400
Subject: [PATCH] [w32handle] Only own first handle if doing WaitHandle.WaitAny
 (#5625)

This is the behaviour on .NET, even if it goes against the documentation at https://msdn.microsoft.com/en-us/library/tdykks7z(v=vs.110).aspx#Anchor_2

Fixes https://bugzilla.xamarin.com/show_bug.cgi?id=59281
---
 mono/metadata/w32handle.c |  9 +++++--
 mono/tests/Makefile.am    |  3 ++-
 mono/tests/bug-59281.cs   | 51 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 60 insertions(+), 3 deletions(-)
 create mode 100644 mono/tests/bug-59281.cs

diff --git a/mono/metadata/w32handle.c b/mono/metadata/w32handle.c
index 98d4ace6d62..654b215538d 100644
--- a/mono/metadata/w32handle.c
+++ b/mono/metadata/w32handle.c
@@ -1218,8 +1218,13 @@ mono_w32handle_wait_multiple (gpointer *handles, gsize nhandles, gboolean waital
 		signalled = (waitall && count == nhandles) || (!waitall && count > 0);
 
 		if (signalled) {
-			for (i = 0; i < nhandles; i++)
-				own_if_signalled (handles [i], &abandoned [i]);
+			for (i = 0; i < nhandles; i++) {
+				if (own_if_signalled (handles [i], &abandoned [i]) && !waitall) {
+					/* if we are calling WaitHandle.WaitAny, .NET only owns the first one; it matters for Mutex which
+					 * throw AbandonedMutexException in case we owned it but didn't release it */
+					break;
+				}
+			}
 		}
 
 		mono_w32handle_unlock_handles (handles, nhandles);
diff --git a/mono/tests/Makefile.am b/mono/tests/Makefile.am
index 729b663f91b..77f06635dde 100755
--- a/mono/tests/Makefile.am
+++ b/mono/tests/Makefile.am
@@ -519,7 +519,8 @@ TESTS_CS_SRC=		\
 	imt_big_iface_test.cs \
 	bug-58782-plain-throw.cs \
 	bug-58782-capture-and-throw.cs \
-	recursive-struct-arrays.cs
+	recursive-struct-arrays.cs \
+	bug-59281.cs
 
 if AMD64
 TESTS_CS_SRC += async-exc-compilation.cs finally_guard.cs finally_block_ending_in_dead_bb.cs
diff --git a/mono/tests/bug-59281.cs b/mono/tests/bug-59281.cs
new file mode 100644
index 00000000000..94250c277a7
--- /dev/null
+++ b/mono/tests/bug-59281.cs
@@ -0,0 +1,51 @@
+using System;
+using System.Threading;
+
+class Driver
+{
+
+	static readonly Mutex[] mutexes = new Mutex[2];
+
+	public static void Main(string[] args)
+	{
+		for (int i = 0; i < mutexes.Length; i++) {
+			mutexes [i] = new Mutex();
+		}
+
+		Thread thread1 = new Thread(() => {
+			for (int i = 0; i < 1; i++) {
+				int idx = -1;
+				try {
+					idx = WaitHandle.WaitAny (mutexes);
+					Console.WriteLine($"Thread 1 iter: {i} with mutex: {idx}");
+				} finally {
+					if (idx != -1)
+						mutexes [idx].ReleaseMutex();
+				}
+			}
+
+			Console.WriteLine("Thread 1 ended");
+		});
+
+		thread1.Start();
+		thread1.Join();
+
+		Thread thread2 = new Thread(() => {
+			for (int i = 0; i < 1000; i++) {
+				int idx = -1;
+				try {
+					idx = WaitHandle.WaitAny (mutexes);
+					Console.WriteLine($"Thread 2 iter: {i} with mutex: {idx}");
+				} finally {
+					if (idx != -1)
+						mutexes [idx].ReleaseMutex();
+				}
+			}
+
+			Console.WriteLine("Thread 2 ended");
+		});
+
+		thread2.Start();
+		thread2.Join();
+	}
+}
\ No newline at end of file
-- 
2.25.1