* Fixed incorrect check in condition_variable_interrupt_thread().

Condition variables would never be interrupted.
* ConditionVariableEntry::Add() did not correctly insert the entry into
  the per-thread list of entries (the next link of the previous entry
  was not adjusted), which could leave the entry unnotified when the
  previous entry was notified, thus leaving it in the respective
  condition variable's list after the end of its life time. This should
  fix a crashing bug I rarely encountered.
* Added debug checks in the PrivateConditionVariableEntry
  constructor/destructor that should have helped me to find
  forementioned bug hours earlier, had I been bright enough to realize
  that I didn't include <debug.h> and those KDEBUG guarded checks were
  never executed. :-/


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22151 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/kernel/condition_variable.cpp

@@ -107,6 +107,8 @@ PrivateConditionVariableEntry::Add(const void* object,
 	if (threadNext) {
 		fThreadPrevious = threadNext->fThreadPrevious;
 		threadNext->fThreadPrevious = this;
+		if (fThreadPrevious)
+			fThreadPrevious->fThreadNext = this;
 	} else
 		fThreadPrevious = NULL;
 
@@ -399,7 +401,7 @@ condition_variable_interrupt_thread(struct thread* thread)
 	// re-get the thread and do the checks again
 	thread = thread_get_thread_struct_locked(threadID);
 
-	if (thread != NULL || thread->state != B_THREAD_WAITING
+	if (thread == NULL || thread->state != B_THREAD_WAITING
 		|| thread->condition_variable_entry == NULL) {
 		return B_BAD_VALUE;
 	}
@@ -417,6 +419,7 @@ condition_variable_interrupt_thread(struct thread* thread)
 	PrivateConditionVariableEntry::Private(*entry).SetResult(B_INTERRUPTED);
 
 	// remove all of the thread's entries from their variables
+	ASSERT(entry->ThreadPrevious() == NULL);
 	while (entry) {
 		PrivateConditionVariableEntry::Private(*entry).Remove();
 		entry = entry->ThreadNext();