Linux: Add gettid system call wrapper [BZ #6399]

This commit adds gettid to <unistd.h> on Linux, and not to the
kernel-independent GNU API.

gettid is now supportable on Linux because too many things assume a
1:1 mapping between libpthread threads and kernel threads.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 129 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/tst-gettid-kill.c b/sysdeps/unix/sysv/linux/tst-gettid-kill.c
new file mode 100644
index 0000000000..98a7c2769e
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-gettid-kill.c
@@ -0,0 +1,129 @@
+/* Verify the interaction of kill and thread groups.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This test demonstrates that a signal which is sent to a specified
+   thread ID using the kill function is delivered to the entire thread
+   group (as if it had been sent to the process group).  */
+
+#include <errno.h>
+#include <signal.h>
+#include <support/check.h>
+#include <support/xsignal.h>
+#include <support/xthread.h>
+#include <support/xunistd.h>
+
+/* Signal set containing SIGUSR1.  */
+static sigset_t sigusr1_set;
+
+/* Used to synchronize the threads.  */
+static pthread_barrier_t barrier;
+
+/* TID of the thread to which the signal is sent.  */
+static pid_t target_tid;
+
+/* Thread which is expected to receive the SIGUSR1 signal.  */
+static pthread_t signal_thread;
+
+/* Pipe used to block and terminate the signal thread.  */
+static int pipe_signal[2];
+
+static volatile sig_atomic_t handler_tid;
+
+static void
+sigusr1_handler (int signo)
+{
+  TEST_COMPARE (signo, SIGUSR1);
+  TEST_VERIFY (pthread_self () == signal_thread);
+  TEST_COMPARE (handler_tid, 0);
+  handler_tid = gettid ();
+  TEST_VERIFY (handler_tid > 0);
+  /* Ensure that the read system call in thread_read exits if the
+     signal is delivered before the system call is invoked.  */
+  char ch = 'X';
+  xwrite (pipe_signal[1], &ch, 1);
+}
+
+/* Thread which calls pause without expecting it to return.  The TID
+   of this thread is used as the target in the kill function call.  */
+static void *
+thread_pause_noreturn (void *closure)
+{
+  target_tid = gettid ();
+  TEST_VERIFY (target_tid > 0);
+  xpthread_barrier_wait (&barrier);
+  pause ();
+  FAIL_EXIT1 ("The pause function returned");
+  return NULL;
+}
+
+/* Thread which is expected to receive the signal.  */
+static void *
+thread_read_signal (void *closure)
+{
+  xpthread_sigmask (SIG_UNBLOCK, &sigusr1_set, NULL);
+  xpthread_barrier_wait (&barrier);
+  TEST_VERIFY (target_tid > 0);
+  TEST_VERIFY (gettid () != target_tid);
+  char ch;
+  ssize_t ret = read (pipe_signal[0], &ch, 1);
+  if (ret == 1)
+    /* The signal was delivered before we entered the read system
+       call.  */
+    TEST_COMPARE (ch, 'X');
+  else
+    {
+      /* The signal was delivered while blocked in the read system
+         call.  */
+      TEST_COMPARE (ret, -1);
+      TEST_COMPARE (errno, EINTR);
+    }
+  TEST_COMPARE (handler_tid, gettid ());
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  /* Block the SIGUSR1 signal in all threads.  */
+  sigemptyset (&sigusr1_set);
+  sigaddset (&sigusr1_set, SIGUSR1);
+  xpthread_sigmask (SIG_BLOCK, &sigusr1_set, NULL);
+
+  xsignal (SIGUSR1, sigusr1_handler);
+  xpipe (pipe_signal);
+
+  xpthread_barrier_init (&barrier, NULL, 3);
+
+  pthread_t target_thread
+    = xpthread_create (NULL, thread_pause_noreturn, NULL);
+  signal_thread = xpthread_create (NULL, thread_read_signal, NULL);
+  xpthread_barrier_wait (&barrier);
+
+  /* Send the SIGUSR1 signal to the thread which has it blocked, and
+     expect it to be delivered to the other thread.  */
+  TEST_COMPARE (kill (target_tid, SIGUSR1), 0);
+
+  xpthread_join (signal_thread);
+  xpthread_cancel (target_thread);
+  xpthread_join (target_thread);
+
+  xpthread_barrier_destroy (&barrier);
+  return 0;
+}
+
+#include <support/test-driver.c>