nptl: Handle spurious EINTR when thread cancellation is disabled (BZ#29029)

Some Linux interfaces never restart after being interrupted by a signal
handler, regardless of the use of SA_RESTART [1].  It means that for
pthread cancellation, if the target thread disables cancellation with
pthread_setcancelstate and calls such interfaces (like poll or select),
it should not see spurious EINTR failures due the internal SIGCANCEL.

However recent changes made pthread_cancel to always sent the internal
signal, regardless of the target thread cancellation status or type.
To fix it, the previous semantic is restored, where the cancel signal
is only sent if the target thread has cancelation enabled in
asynchronous mode.

The cancel state and cancel type is moved back to cancelhandling
and atomic operation are used to synchronize between threads.  The
patch essentially revert the following commits:

  8c1c0aae20 nptl: Move cancel type out of cancelhandling
  2b51742531 nptl: Move cancel state out of cancelhandling
  26cfbb7162 nptl: Remove CANCELING_BITMASK

However I changed the atomic operation to follow the internal C11
semantic and removed the MACRO usage, it simplifies a bit the
resulting code (and removes another usage of the old atomic macros).

Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
and powerpc64-linux-gnu.

[1] https://man7.org/linux/man-pages/man7/signal.7.html

Reviewed-by: Florian Weimer <fweimer@redhat.com>
Tested-by: Aurelien Jarno <aurelien@aurel32.net>

2 files changed, 208 insertions, 0 deletions

diff --git a/sysdeps/pthread/Makefile b/sysdeps/pthread/Makefile
index 318dfdc04a..e901c51df0 100644
--- a/sysdeps/pthread/Makefile
+++ b/sysdeps/pthread/Makefile
@@ -69,6 +69,7 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
 	 tst-cancel12 tst-cancel13 tst-cancel14 tst-cancel15 tst-cancel16 \
 	 tst-cancel18 tst-cancel19 tst-cancel20 tst-cancel21 \
 	 tst-cancel22 tst-cancel23 tst-cancel26 tst-cancel27 tst-cancel28 \
+	 tst-cancel29 \
 	 tst-cleanup0 tst-cleanup1 tst-cleanup2 tst-cleanup3 \
 	 tst-clock1 \
 	 tst-cond-except \
diff --git a/sysdeps/pthread/tst-cancel29.c b/sysdeps/pthread/tst-cancel29.c
new file mode 100644
index 0000000000..4f0d99e002
--- /dev/null
+++ b/sysdeps/pthread/tst-cancel29.c
@@ -0,0 +1,207 @@
+/* Check if a thread that disables cancellation and which call functions
+   that might be interrupted by a signal do not see the internal SIGCANCEL.
+
+   Copyright (C) 2022 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <array_length.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <poll.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xthread.h>
+#include <sys/socket.h>
+#include <signal.h>
+#include <stdio.h>
+#include <unistd.h>
+
+/* On Linux some interfaces are never restarted after being interrupted by
+   a signal handler, regardless of the use of SA_RESTART.  It means that
+   if asynchronous cancellation is not enabled, the pthread_cancel can not
+   set the internal SIGCANCEL otherwise the interface might see a spurious
+   EINTR failure.  */
+
+static pthread_barrier_t b;
+
+/* Cleanup handling test.  */
+static int cl_called;
+static void
+cl (void *arg)
+{
+  ++cl_called;
+}
+
+static void *
+tf_sigtimedwait (void *arg)
+{
+  pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, NULL);
+  xpthread_barrier_wait (&b);
+
+  int r;
+  pthread_cleanup_push (cl, NULL);
+
+  sigset_t mask;
+  sigemptyset (&mask);
+  r = sigtimedwait (&mask, NULL, &(struct timespec) { 0, 250000000 });
+  if (r != -1)
+    return (void*) -1;
+  if (errno != EAGAIN)
+    return (void*) -2;
+
+  pthread_cleanup_pop (0);
+  return NULL;
+}
+
+static void *
+tf_poll (void *arg)
+{
+  pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, NULL);
+  xpthread_barrier_wait (&b);
+
+  int r;
+  pthread_cleanup_push (cl, NULL);
+
+  r = poll (NULL, 0, 250);
+  if (r != 0)
+    return (void*) -1;
+
+  pthread_cleanup_pop (0);
+  return NULL;
+}
+
+static void *
+tf_ppoll (void *arg)
+{
+  pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, NULL);
+
+  xpthread_barrier_wait (&b);
+
+  int r;
+  pthread_cleanup_push (cl, NULL);
+
+  r = ppoll (NULL, 0, &(struct timespec) { 0, 250000000 }, NULL);
+  if (r != 0)
+    return (void*) -1;
+
+  pthread_cleanup_pop (0);
+  return NULL;
+}
+
+static void *
+tf_select (void *arg)
+{
+  pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, NULL);
+  xpthread_barrier_wait (&b);
+
+  int r;
+  pthread_cleanup_push (cl, NULL);
+
+  r = select (0, NULL, NULL, NULL, &(struct timeval) { 0, 250000 });
+  if (r != 0)
+    return (void*) -1;
+
+  pthread_cleanup_pop (0);
+  return NULL;
+}
+
+static void *
+tf_pselect (void *arg)
+{
+  pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, NULL);
+  xpthread_barrier_wait (&b);
+
+  int r;
+  pthread_cleanup_push (cl, NULL);
+
+  r = pselect (0, NULL, NULL, NULL, &(struct timespec) { 0, 250000000 }, NULL);
+  if (r != 0)
+    return (void*) -1;
+
+  pthread_cleanup_pop (0);
+  return NULL;
+}
+
+static void *
+tf_clock_nanosleep (void *arg)
+{
+  pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, NULL);
+  xpthread_barrier_wait (&b);
+
+  int r;
+  pthread_cleanup_push (cl, NULL);
+
+  r = clock_nanosleep (CLOCK_REALTIME, 0, &(struct timespec) { 0, 250000000 },
+		       NULL);
+  if (r != 0)
+    return (void*) -1;
+
+  pthread_cleanup_pop (0);
+  return NULL;
+}
+
+struct cancel_test_t
+{
+  const char *name;
+  void * (*cf) (void *);
+} tests[] =
+{
+  { "sigtimedwait",    tf_sigtimedwait,    },
+  { "poll",            tf_poll,            },
+  { "ppoll",           tf_ppoll,           },
+  { "select",          tf_select,          },
+  { "pselect",         tf_pselect  ,       },
+  { "clock_nanosleep", tf_clock_nanosleep, },
+};
+
+static int
+do_test (void)
+{
+  for (int i = 0; i < array_length (tests); i++)
+    {
+      xpthread_barrier_init (&b, NULL, 2);
+
+      cl_called = 0;
+
+      pthread_t th = xpthread_create (NULL, tests[i].cf, NULL);
+
+      xpthread_barrier_wait (&b);
+
+      struct timespec ts = { .tv_sec = 0, .tv_nsec = 100000000 };
+      while (nanosleep (&ts, &ts) != 0)
+	continue;
+
+      xpthread_cancel (th);
+
+      void *status = xpthread_join (th);
+      if (status != NULL)
+	printf ("test '%s' failed: %" PRIdPTR "\n", tests[i].name,
+		(intptr_t) status);
+      TEST_VERIFY (status == NULL);
+
+      xpthread_barrier_destroy (&b);
+
+      TEST_COMPARE (cl_called, 0);
+
+      printf ("in-time cancel test of '%s' successful\n", tests[i].name);
+    }
+
+  return 0;
+}
+
+#include <support/test-driver.c>