LibC+LibPthread: Implement pthread_atfork()

This required a bit of rearchitecture, as pthread_atfork() required a
mutex, and duplicating a mutex impl for it was silly.
As such, this patch moves some standalone bits of pthread into LibC and
uses those to implement atfork().
It should be noted that for programs that don't use atfork(), this
mechanism only costs two atomic loads (as opposed to the normal mutex
lock+unlock) :^)

1 files changed, 53 insertions, 0 deletions

diff --git a/Userland/Libraries/LibC/bits/pthread_integration.h b/Userland/Libraries/LibC/bits/pthread_integration.h
new file mode 100644
index 0000000000..5a7b5e24e6
--- /dev/null
+++ b/Userland/Libraries/LibC/bits/pthread_integration.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+void __pthread_fork_prepare(void);
+void __pthread_fork_child(void);
+void __pthread_fork_parent(void);
+void __pthread_fork_atfork_register_prepare(void (*)(void));
+void __pthread_fork_atfork_register_parent(void (*)(void));
+void __pthread_fork_atfork_register_child(void (*)(void));
+
+int __pthread_mutex_lock(void*);
+int __pthread_mutex_unlock(void*);
+int __pthread_mutex_init(void*, const void*);
+
+int __pthread_self();
+
+#define __PTHREAD_MUTEX_NORMAL 0
+#define __PTHREAD_MUTEX_RECURSIVE 1
+#define __PTHREAD_MUTEX_INITIALIZER     \
+    {                                   \
+        0, 0, 0, __PTHREAD_MUTEX_NORMAL \
+    }
+
+__END_DECLS