From 0cb2617fa541dbcf53188b492a34f96ad0cf4ef8 Mon Sep 17 00:00:00 2001
From: Ingo Weinhold <ingo_weinhold@gmx.de>
Date: Mon, 2 Jun 2008 04:34:09 +0000
Subject: [PATCH] Before starting to wait the undertaker does now check whether
 there's already a dead thread available. Fixes a race condition.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25754 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 src/system/kernel/thread.cpp | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/system/kernel/thread.cpp b/src/system/kernel/thread.cpp
index 1035dd3a1e..4e1cb2195e 100644
--- a/src/system/kernel/thread.cpp
+++ b/src/system/kernel/thread.cpp
@@ -540,21 +540,21 @@ undertaker(void* /*args*/)
 {
 	while (true) {
 		// wait for a thread to bury
-		ConditionVariableEntry conditionEntry;
-
 		InterruptsSpinLocker locker(thread_spinlock);
-		sUndertakerCondition.Add(&conditionEntry);
-		locker.Unlock();
 
-		conditionEntry.Wait();
+		while (sUndertakerEntries.IsEmpty()) {
+			ConditionVariableEntry conditionEntry;
+			sUndertakerCondition.Add(&conditionEntry);
+			locker.Unlock();
+
+			conditionEntry.Wait();
+
+			locker.Lock();
+		}
 
-		locker.Lock();
 		UndertakerEntry* _entry = sUndertakerEntries.RemoveHead();
 		locker.Unlock();
 
-		if (_entry == NULL)
-			continue;
-
 		UndertakerEntry entry = *_entry;
 			// we need a copy, since the original entry is on the thread's stack