From ff443c9f5e0631e263b0e3515d5140f10dbbe8ca Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Thu, 9 Jan 2014 00:57:41 +0100
Subject: [PATCH] Thread-secure dregister(3) and dunregister(3).

---
 libc/dirent/dcloseall.cpp   | 2 ++
 libc/dirent/dregister.cpp   | 3 +++
 libc/dirent/dunregister.cpp | 5 +++++
 3 files changed, 10 insertions(+)

diff --git a/libc/dirent/dcloseall.cpp b/libc/dirent/dcloseall.cpp
index 84ef862e..0afeeeae 100644
--- a/libc/dirent/dcloseall.cpp
+++ b/libc/dirent/dcloseall.cpp
@@ -31,6 +31,8 @@ extern "C" { DIR* __firstdir = NULL; }
 extern "C" int dcloseall(void)
 {
 	int result = 0;
+	// We do not lock __firstdir_lock here because this function is called on
+	// process termination and only one thread can call exit(3).
 	while ( __firstdir )
 		result |= closedir(__firstdir);
 	return result ? EOF : 0;
diff --git a/libc/dirent/dregister.cpp b/libc/dirent/dregister.cpp
index 6e05106e..2026fd9c 100644
--- a/libc/dirent/dregister.cpp
+++ b/libc/dirent/dregister.cpp
@@ -24,6 +24,9 @@
 
 #include <dirent.h>
 #include <DIR.h>
+#include <pthread.h>
+
+extern "C" pthread_mutex_t __dirname_lock;
 
 extern "C" void dregister(DIR* dir)
 {
diff --git a/libc/dirent/dunregister.cpp b/libc/dirent/dunregister.cpp
index 2b1d544f..6a3a7e22 100644
--- a/libc/dirent/dunregister.cpp
+++ b/libc/dirent/dunregister.cpp
@@ -24,11 +24,15 @@
 
 #include <dirent.h>
 #include <DIR.h>
+#include <pthread.h>
+
+extern "C" { pthread_mutex_t __dirname_lock = PTHREAD_MUTEX_INITIALIZER; }
 
 extern "C" void dunregister(DIR* dir)
 {
 	if ( !(dir->flags & _DIR_REGISTERED) )
 		return;
+	pthread_mutex_lock(&__dirname_lock);
 	if ( !dir->prev )
 		__firstdir = dir->next;
 	if ( dir->prev )
@@ -36,4 +40,5 @@ extern "C" void dunregister(DIR* dir)
 	if ( dir->next )
 		dir->next->prev = dir->prev;
 	dir->flags &= ~_DIR_REGISTERED;
+	pthread_mutex_unlock(&__dirname_lock);
 }