Unregister pthread_atfork handlers on dlclose()

Change-Id: I326fdf6bb06bed12743f08980b5c69d849c015b8

9 files changed, 141 insertions, 32 deletions

diff --git a/libc/Android.mk b/libc/Android.mk
index 4a199e7..8ed969f 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -63,6 +63,7 @@ libc_common_src_files := \
     stdio/sprintf.c \
     stdio/stdio.c \
     stdio/stdio_ext.cpp \
+    stdlib/atexit.c \
     stdlib/exit.c \
 
 # Fortify implementations of libc functions.
@@ -481,7 +482,6 @@ libc_upstream_openbsd_ndk_src_files := \
     upstream-openbsd/lib/libc/stdio/wprintf.c \
     upstream-openbsd/lib/libc/stdio/wscanf.c \
     upstream-openbsd/lib/libc/stdio/wsetup.c \
-    upstream-openbsd/lib/libc/stdlib/atexit.c \
     upstream-openbsd/lib/libc/stdlib/atoi.c \
     upstream-openbsd/lib/libc/stdlib/atol.c \
     upstream-openbsd/lib/libc/stdlib/atoll.c \
diff --git a/libc/arch-arm64/bionic/crtbegin.c b/libc/arch-arm64/bionic/crtbegin.c
index fec0b11..7e2c5d7 100644
--- a/libc/arch-arm64/bionic/crtbegin.c
+++ b/libc/arch-arm64/bionic/crtbegin.c
@@ -67,3 +67,4 @@ __asm__ (
 
 #include "../../arch-common/bionic/__dso_handle.h"
 #include "../../arch-common/bionic/atexit.h"
+#include "../../arch-common/bionic/pthread_atfork.h"
diff --git a/libc/arch-common/bionic/crtbegin.c b/libc/arch-common/bionic/crtbegin.c
index fa9f3f3..c46405c 100644
--- a/libc/arch-common/bionic/crtbegin.c
+++ b/libc/arch-common/bionic/crtbegin.c
@@ -59,6 +59,7 @@ void _start() {
 
 #include "__dso_handle.h"
 #include "atexit.h"
+#include "pthread_atfork.h"
 #ifdef __i386__
 # include "../../arch-x86/bionic/__stack_chk_fail_local.h"
 #endif
diff --git a/libc/arch-common/bionic/crtbegin_so.c b/libc/arch-common/bionic/crtbegin_so.c
index 641e45a..3754363 100644
--- a/libc/arch-common/bionic/crtbegin_so.c
+++ b/libc/arch-common/bionic/crtbegin_so.c
@@ -56,6 +56,7 @@ void __on_dlclose() {
 # include "__dso_handle_so.h"
 # include "atexit.h"
 #endif
+#include "pthread_atfork.h"
 #ifdef __i386__
 # include "../../arch-x86/bionic/__stack_chk_fail_local.h"
 #endif
diff --git a/libc/arch-common/bionic/pthread_atfork.h b/libc/arch-common/bionic/pthread_atfork.h
new file mode 100644
index 0000000..0c48a12
--- /dev/null
+++ b/libc/arch-common/bionic/pthread_atfork.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+extern void* __dso_handle;
+
+extern int __register_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(void), void* dso);
+
+#ifndef _LIBC
+// Libc used to export this in previous versions, therefore it needs
+// to remain global for binary compatibility.
+__attribute__ ((visibility ("hidden")))
+#endif
+int pthread_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(void)) {
+  return __register_atfork(prepare, parent, child, &__dso_handle);
+}
+
diff --git a/libc/arch-mips/bionic/crtbegin.c b/libc/arch-mips/bionic/crtbegin.c
index 50e9eeb..d72ec7b 100644
--- a/libc/arch-mips/bionic/crtbegin.c
+++ b/libc/arch-mips/bionic/crtbegin.c
@@ -92,3 +92,4 @@ __asm__ (
 
 #include "../../arch-common/bionic/__dso_handle.h"
 #include "../../arch-common/bionic/atexit.h"
+#include "../../arch-common/bionic/pthread_atfork.h"
diff --git a/libc/bionic/pthread_atfork.cpp b/libc/bionic/pthread_atfork.cpp
index d1c4ad0..093ffd2 100644
--- a/libc/bionic/pthread_atfork.cpp
+++ b/libc/bionic/pthread_atfork.cpp
@@ -30,6 +30,8 @@
 #include <pthread.h>
 #include <stdlib.h>
 
+#include "private/bionic_macros.h"
+
 struct atfork_t {
   atfork_t* next;
   atfork_t* prev;
@@ -37,79 +39,143 @@ struct atfork_t {
   void (*prepare)(void);
   void (*child)(void);
   void (*parent)(void);
+
+  void* dso_handle;
 };
 
-struct atfork_list_t {
-  atfork_t* first;
-  atfork_t* last;
+class atfork_list_t {
+ public:
+  atfork_list_t() : first_(nullptr), last_(nullptr) {}
+
+  template<typename F>
+  void walk_forward(F f) {
+    for (atfork_t* it = first_; it != nullptr; it = it->next) {
+      f(it);
+    }
+  }
+
+  template<typename F>
+  void walk_backwards(F f) {
+    for (atfork_t* it = last_; it != nullptr; it = it->prev) {
+      f(it);
+    }
+  }
+
+  void push_back(atfork_t* entry) {
+    entry->next = nullptr;
+    entry->prev = last_;
+    if (entry->prev != nullptr) {
+      entry->prev->next = entry;
+    }
+    if (first_ == nullptr) {
+      first_ = entry;
+    }
+    last_ = entry;
+  }
+
+  template<typename F>
+  void remove_if(F predicate) {
+    atfork_t* it = first_;
+    while (it != nullptr) {
+      if (predicate(it)) {
+        atfork_t* entry = it;
+        it = it->next;
+        remove(entry);
+      } else {
+        it = it->next;
+      }
+    }
+  }
+
+ private:
+  void remove(atfork_t* entry) {
+    if (entry->prev != nullptr) {
+      entry->prev->next = entry->next;
+    } else {
+      first_ = entry->next;
+    }
+
+    if (entry->next != nullptr) {
+      entry->next->prev = entry->prev;
+    } else {
+      last_ = entry->prev;
+    }
+
+    free(entry);
+  }
+
+  atfork_t* first_;
+  atfork_t* last_;
+
+  DISALLOW_COPY_AND_ASSIGN(atfork_list_t);
 };
 
 static pthread_mutex_t g_atfork_list_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
-static atfork_list_t g_atfork_list = { NULL, NULL };
+static atfork_list_t g_atfork_list;
 
 void __bionic_atfork_run_prepare() {
   // We lock the atfork list here, unlock it in the parent, and reset it in the child.
   // This ensures that nobody can modify the handler array between the calls
   // to the prepare and parent/child handlers.
-  //
-  // TODO: If a handler tries to mutate the list, they'll block. We should probably copy
-  // the list before forking, and have prepare, parent, and child all work on the consistent copy.
   pthread_mutex_lock(&g_atfork_list_mutex);
 
   // Call pthread_atfork() prepare handlers. POSIX states that the prepare
   // handlers should be called in the reverse order of the parent/child
   // handlers, so we iterate backwards.
-  for (atfork_t* it = g_atfork_list.last; it != NULL; it = it->prev) {
-    if (it->prepare != NULL) {
+  g_atfork_list.walk_backwards([](atfork_t* it) {
+    if (it->prepare != nullptr) {
       it->prepare();
     }
-  }
+  });
 }
 
 void __bionic_atfork_run_child() {
-  for (atfork_t* it = g_atfork_list.first; it != NULL; it = it->next) {
-    if (it->child != NULL) {
+  g_atfork_list.walk_forward([](atfork_t* it) {
+    if (it->child != nullptr) {
       it->child();
     }
-  }
+  });
 
   g_atfork_list_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
 }
 
 void __bionic_atfork_run_parent() {
-  for (atfork_t* it = g_atfork_list.first; it != NULL; it = it->next) {
-    if (it->parent != NULL) {
+  g_atfork_list.walk_forward([](atfork_t* it) {
+    if (it->parent != nullptr) {
       it->parent();
     }
-  }
+  });
 
   pthread_mutex_unlock(&g_atfork_list_mutex);
 }
 
-int pthread_atfork(void (*prepare)(void), void (*parent)(void), void(*child)(void)) {
+// __register_atfork is the name used by glibc
+extern "C" int __register_atfork(void (*prepare)(void), void (*parent)(void),
+                                 void(*child)(void), void* dso) {
   atfork_t* entry = reinterpret_cast<atfork_t*>(malloc(sizeof(atfork_t)));
-  if (entry == NULL) {
+  if (entry == nullptr) {
     return ENOMEM;
   }
 
   entry->prepare = prepare;
   entry->parent = parent;
   entry->child = child;
+  entry->dso_handle = dso;
 
   pthread_mutex_lock(&g_atfork_list_mutex);
 
-  // Append 'entry' to the list.
-  entry->next = NULL;
-  entry->prev = g_atfork_list.last;
-  if (entry->prev != NULL) {
-    entry->prev->next = entry;
-  }
-  if (g_atfork_list.first == NULL) {
-    g_atfork_list.first = entry;
-  }
-  g_atfork_list.last = entry;
+  g_atfork_list.push_back(entry);
 
   pthread_mutex_unlock(&g_atfork_list_mutex);
 
   return 0;
 }
+
+extern "C" __LIBC_HIDDEN__ void __unregister_atfork(void* dso) {
+  pthread_mutex_lock(&g_atfork_list_mutex);
+  g_atfork_list.remove_if([&](const atfork_t* entry) {
+    return entry->dso_handle == dso;
+  });
+  pthread_mutex_unlock(&g_atfork_list_mutex);
+}
+
diff --git a/libc/upstream-openbsd/lib/libc/stdlib/atexit.c b/libc/stdlib/atexit.c
index 6532b38..df2b1b5 100644
--- a/libc/upstream-openbsd/lib/libc/stdlib/atexit.c
+++ b/libc/stdlib/atexit.c
@@ -35,11 +35,15 @@
 #include <string.h>
 #include <unistd.h>
 #include "atexit.h"
-#include "thread_private.h"
+#include "private/thread_private.h"
 
 struct atexit *__atexit;
 static int restartloop;
 
+/* BEGIN android-changed: __unregister_atfork is used by __cxa_finalize */
+extern void __unregister_atfork(void* dso);
+/* END android-changed */
+
 /*
  * Function pointers are stored in a linked list of pages. The list
  * is initially empty, and pages are allocated on demand. The first
@@ -62,7 +66,7 @@ __cxa_atexit(void (*func)(void *), void *arg, void *dso)
 {
 	struct atexit *p = __atexit;
 	struct atexit_fn *fnp;
-	int pgsize = getpagesize();
+	size_t pgsize = getpagesize();
 	int ret = -1;
 
 	if (pgsize < sizeof(*p))
@@ -161,6 +165,12 @@ restart:
 		__atexit = NULL;
 	}
 	_ATEXIT_UNLOCK();
+
+  /* BEGIN android-changed: call __unregister_atfork if dso is not null */
+  if (dso != NULL) {
+    __unregister_atfork(dso);
+  }
+  /* END android-changed */
 }
 
 /*
@@ -170,7 +180,7 @@ void
 __atexit_register_cleanup(void (*func)(void))
 {
 	struct atexit *p;
-	int pgsize = getpagesize();
+	size_t pgsize = getpagesize();
 
 	if (pgsize < sizeof(*p))
 		return;
diff --git a/libc/upstream-openbsd/lib/libc/stdlib/atexit.h b/libc/stdlib/atexit.h
index 3de2aa3..3de2aa3 100644
--- a/libc/upstream-openbsd/lib/libc/stdlib/atexit.h
+++ b/libc/stdlib/atexit.h