1 files changed, 88 insertions, 0 deletions
diff --git a/gdb/testsuite/gdb.threads/vfork-multi-thread.c b/gdb/testsuite/gdb.threads/vfork-multi-thread.c
new file mode 100644
index 00000000000..7e38f8a9939
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/vfork-multi-thread.c
@@ -0,0 +1,88 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2022 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <assert.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+static volatile int release_vfork = 0;
+static volatile int release_main = 0;
+
+static void *
+vforker (void *arg)
+{
+  while (!release_vfork)
+    usleep (1);
+
+  pid_t pid = vfork ();
+  if (pid == 0)
+    {
+      /* A vfork child is not supposed to mess with the state of the program,
+	 but it is helpful for the purpose of this test.  */
+      release_main = 1;
+      _exit(7);
+    }
+
+  int stat;
+  int ret = waitpid (pid, &stat, 0);
+  assert (ret == pid);
+  assert (WIFEXITED (stat));
+  assert (WEXITSTATUS (stat) == 7);
+
+  return NULL;
+}
+
+static void
+should_break_here (void)
+{}
+
+int
+main (void)
+{
+
+  pthread_t thread;
+  int ret = pthread_create (&thread, NULL, vforker, NULL);
+  assert (ret == 0);
+
+  /* We break here first, while the thread is stuck on `!release_fork`.  */
+  release_vfork = 1;
+
+  /* We set a breakpoint on should_break_here.
+
+     We then set "release_fork" from the debugger and continue.  The main
+     thread hangs on `!release_main` while the non-main thread vforks.  During
+     the window of time where the two processes have a shared address space
+     (after vfork, before _exit), GDB removes the breakpoints from the address
+     space.  During that window, only the vfork-ing thread (the non-main
+     thread) is frozen by the kernel.  The main thread is free to execute.  The
+     child process sets `release_main`, releasing the main thread. A buggy GDB
+     would let the main thread execute during that window, leading to the
+     breakpoint on should_break_here being missed.  A fixed GDB does not resume
+     the threads of the vforking process other than the vforking thread.  When
+     the vfork child exits, the fixed GDB resumes the main thread, after
+     breakpoints are reinserted, so the breakpoint is not missed.  */
+
+  while (!release_main)
+    usleep (1);
+
+  should_break_here ();
+
+  pthread_join (thread, NULL);
+
+  return 6;
+}