commit 8bfaac0f8ad5f280d1f893fe682e007dd0820692
author Dimitry Ivanov <dimitry@google.com> Tue Nov 08 20:59:42 2016 +0000
committer Gerrit Code Review <noreply-gerritcodereview@google.com> Tue Nov 08 20:59:42 2016 +0000
tree 7ef8d9c77682ba3abd7a1ee3c5c4857c5480fb42
parent bfc6ce6424488b199cf58cf478c405ac6308c346
parent f6a21bfac5abf7c6fc121ca1caa78528690a25dd

Merge "Eliminate deadlock in forked child due to delayed resetting mutex lock"

libc/bionic/pthread_atfork.cpp

diff --git a/libc/bionic/pthread_atfork.cpp b/libc/bionic/pthread_atfork.cpp
index 2200a6c..84e511c 100644
--- a/libc/bionic/pthread_atfork.cpp
+++ b/libc/bionic/pthread_atfork.cpp
@@ -130,13 +130,15 @@
 }
 
 void __bionic_atfork_run_child() {
+  g_atfork_list_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
+
+  pthread_mutex_lock(&g_atfork_list_mutex);
   g_atfork_list.walk_forward([](atfork_t* it) {
     if (it->child != nullptr) {
       it->child();
     }
   });
-
-  g_atfork_list_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
+  pthread_mutex_unlock(&g_atfork_list_mutex);
 }
 
 void __bionic_atfork_run_parent() {

tests/pthread_dlfcn_test.cpp

diff --git a/tests/pthread_dlfcn_test.cpp b/tests/pthread_dlfcn_test.cpp
index 64423da..1c733fe 100644
--- a/tests/pthread_dlfcn_test.cpp
+++ b/tests/pthread_dlfcn_test.cpp
@@ -37,6 +37,11 @@
 static void AtForkChild3() { g_atfork_child_calls = (g_atfork_child_calls * 10) + 3; }
 static void AtForkChild4() { g_atfork_child_calls = (g_atfork_child_calls * 10) + 4; }
 
+static void* g_atfork_test_handle = nullptr;
+static void AtForkPrepare() {}
+static void AtForkParent() {}
+static void AtForkChild() { dlclose(g_atfork_test_handle); g_atfork_test_handle = dlopen("libtest_pthread_atfork.so", RTLD_NOW | RTLD_LOCAL); }
+
 TEST(pthread, pthread_atfork_with_dlclose) {
   ASSERT_EQ(0, pthread_atfork(AtForkPrepare1, AtForkParent1, AtForkChild1));
 
@@ -82,3 +87,28 @@
 
   AssertChildExited(pid, 0);
 }
+
+TEST(pthread, pthread_atfork_child_with_dlclose) {
+
+  g_atfork_test_handle = dlopen("libtest_pthread_atfork.so", RTLD_NOW | RTLD_LOCAL);
+  ASSERT_TRUE(g_atfork_test_handle != nullptr) << dlerror();
+  typedef int (*fn_t)(void (*)(void), void (*)(void), void (*)(void));
+  fn_t fn = reinterpret_cast<fn_t>(dlsym(g_atfork_test_handle, "proxy_pthread_atfork"));
+  ASSERT_TRUE(fn != nullptr) << dlerror();
+  // the library registers 2 additional atfork handlers in a constructor
+
+  ASSERT_EQ(0, pthread_atfork(AtForkPrepare, AtForkParent, AtForkChild));
+
+  pid_t pid = fork();
+
+  ASSERT_NE(-1, pid) << strerror(errno);
+
+  if (pid == 0) {
+    _exit(0);
+  }
+
+  AssertChildExited(pid, 0);
+
+  EXPECT_EQ(0, dlclose(g_atfork_test_handle));
+  g_atfork_test_handle = nullptr;
+}