xserver: add XORG_GTEST_XSERVER_KEEPALIVE environment variable

If set, XServer will ignore Terminate() and Kill() requests, and will not
die if the parent process dies. This enables a user to hook up gdb to a
server, wait for the test case to trigger some code in the server and
continue debugging from there, without the test case terminating the server.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Chase Douglas <chase.douglas@ubuntu.com>

3 files changed, 82 insertions, 0 deletions

diff --git a/README b/README
index 6c660b0..53475db 100644
--- a/README
+++ b/README
@@ -78,6 +78,10 @@ Environment variables
 ---------------------
 XORG_GTEST_XSERVER_SIGSTOP
   If set, an XServer object will raise a SIGSTOP signal after startup.
+XORG_GTEST_XSERVER_KEEPALIVE
+  If set, the XServer object will ignore calls to Terminate() or Kill().
+  This is useful for debugging a server without having the test terminate
+  the process while still looking at gdb output.
 XORG_GTEST_CHILD_STDOUT
   If set to any value, Process::Start() will _not_ close stdout/stdin/stderr
   for the forked child.
diff --git a/src/xserver.cpp b/src/xserver.cpp
index 114f610..d41fcb4 100644
--- a/src/xserver.cpp
+++ b/src/xserver.cpp
@@ -433,6 +433,11 @@ void xorg::testing::XServer::Start(const std::string &program) {
 
   pid_t pid = Fork();
   if (pid == 0) {
+#ifdef __linux
+    if (getenv("XORG_GTEST_XSERVER_KEEPALIVE"))
+      prctl(PR_SET_PDEATHSIG, 0);
+#endif
+
     /* set SIGUSR1 handler to SIG_IGN, XServer tests for this and will
      * send SIGUSR1 when ready */
     sighandler_t old_handler;
@@ -490,6 +495,9 @@ void xorg::testing::XServer::Start(const std::string &program) {
 }
 
 bool xorg::testing::XServer::Terminate(unsigned int timeout) {
+  if (getenv("XORG_GTEST_XSERVER_KEEPALIVE"))
+    return true;
+
   if (!Process::Terminate(timeout)) {
     std::cerr << "Warning: Failed to terminate Xorg server: "
               << std::strerror(errno) << "\n";
@@ -499,6 +507,9 @@ bool xorg::testing::XServer::Terminate(unsigned int timeout) {
 }
 
 bool xorg::testing::XServer::Kill(unsigned int timeout) {
+  if (getenv("XORG_GTEST_XSERVER_KEEPALIVE"))
+    return true;
+
   if (!Process::Kill(timeout)) {
     std::cerr << "Warning: Failed to kill Xorg server: "
               << std::strerror(errno) << "\n";
diff --git a/test/xserver-test.cpp b/test/xserver-test.cpp
index 4088baa..ccbc2e9 100644
--- a/test/xserver-test.cpp
+++ b/test/xserver-test.cpp
@@ -207,6 +207,73 @@ TEST(XServer, IOErrorException)
   }, XIOError);
 }
 
+TEST(XServer, KeepAlive)
+{
+  XORG_TESTCASE("If XORG_GTEST_XSERVER_KEEPALIVE is set,\n"
+                "XServer::Terminate() and XServer::Kill() have no "
+                "effect");
+
+  int pipefd[2];
+  ASSERT_NE(pipe(pipefd), -1);
+
+  if (fork() == 0) {
+    close(pipefd[0]);
+
+    ASSERT_EQ(setenv("XORG_GTEST_XSERVER_KEEPALIVE", "1", 1), 0);
+    ASSERT_TRUE(getenv("XORG_GTEST_XSERVER_KEEPALIVE") != NULL);
+
+    XServer server;
+    server.SetOption("-logfile", "/tmp/Xorg-keepalive.log");
+    server.SetOption("-noreset", "");
+    server.Start();
+    ASSERT_EQ(server.GetState(), Process::RUNNING);
+    ::Display *dpy = XOpenDisplay(server.GetDisplayString().c_str());
+    ASSERT_TRUE(dpy != NULL);
+
+    server.Terminate();
+    ASSERT_EQ(server.GetState(), Process::RUNNING);
+    server.Kill();
+    ASSERT_EQ(server.GetState(), Process::RUNNING);
+
+    char *buffer;
+    ASSERT_GT(asprintf(&buffer, "%d", server.Pid()), 0);
+    ASSERT_EQ(write(pipefd[1], buffer, strlen(buffer)), (int)strlen(buffer));
+    close(pipefd[1]);
+    free(buffer);
+    return;
+  }
+
+  sigset_t sig_mask;
+  sigemptyset(&sig_mask);
+  sigaddset(&sig_mask, SIGCHLD);
+  struct timespec tv = { 1, 0 };
+  sigprocmask(SIG_BLOCK, &sig_mask, NULL);
+
+  /* parent */
+  close(pipefd[1]);
+
+  char buffer[20] = {0};
+  ASSERT_GT(read(pipefd[0], buffer, sizeof(buffer)), 0);
+  close(pipefd[0]);
+
+  /* wait for forked child to die */
+  ASSERT_EQ(sigtimedwait(&sig_mask, NULL, &tv), SIGCHLD);
+
+  pid_t server_pid = atoi(buffer);
+
+  /* server must still be running, kill it */
+  ASSERT_EQ(kill(server_pid, 0), 0);
+  kill(server_pid, SIGTERM);
+
+  int i = 0;
+
+  while(kill(server_pid, 0) == 0 && i++ < 10)
+    usleep(50000);
+
+  ASSERT_EQ(kill(server_pid, 0), -1);
+  ASSERT_EQ(errno, ESRCH);
+}
+
 int main(int argc, char *argv[]) {
   testing::InitGoogleTest(&argc, argv);
   return RUN_ALL_TESTS();