linked-list test: Add test for SIGNAL_SAFE_LIST. (It currently fails.)

* tests/test-asyncsafe-linked_list.sh: New file.
* tests/test-asyncsafe-linked_list.c: New file.
* modules/linked-list-tests (Files): Add them.
(Depends-on): Add thread, yield, nanosleep, sigaction, sigprocmask.
(Makefile.am): Arrange to compile test-asyncsafe-linked_list.c and run
test-asyncsafe-linked_list.sh.

ChangeLog

@@ -1,3 +1,13 @@
+2021-02-15  Bruno Haible  <bruno@clisp.org>
+
+	linked-list test: Add test for SIGNAL_SAFE_LIST. (It currently fails.)
+	* tests/test-asyncsafe-linked_list.sh: New file.
+	* tests/test-asyncsafe-linked_list.c: New file.
+	* modules/linked-list-tests (Files): Add them.
+	(Depends-on): Add thread, yield, nanosleep, sigaction, sigprocmask.
+	(Makefile.am): Arrange to compile test-asyncsafe-linked_list.c and run
+	test-asyncsafe-linked_list.sh.
+
 2021-02-14  Bruno Haible  <bruno@clisp.org>
 
 	simple-atomic: Add tests.

modules/linked-list-tests

@@ -1,12 +1,20 @@
 Files:
 tests/test-linked_list.c
+tests/test-asyncsafe-linked_list.sh
+tests/test-asyncsafe-linked_list.c
 tests/macros.h
 
 Depends-on:
 array-list
+thread
+yield
+nanosleep
+sigaction
+sigprocmask
 
 configure.ac:
 
 Makefile.am:
-TESTS += test-linked_list
+TESTS += test-linked_list test-asyncsafe-linked_list.sh
-check_PROGRAMS += test-linked_list
+check_PROGRAMS += test-linked_list test-asyncsafe-linked_list
+test_asyncsafe_linked_list_LDADD = $(LDADD) @LIBMULTITHREAD@ @YIELD_LIB@

tests/test-asyncsafe-linked_list.c

@@ -0,0 +1,322 @@
+/* Test of async-safe sequential list data type implementation.
+   Copyright (C) 2021 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 <https://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2021.  */
+
+#include <config.h>
+
+/* Work around GCC bug 44511.  */
+#if 4 < __GNUC__ + (3 <= __GNUC_MINOR__)
+# pragma GCC diagnostic ignored "-Wreturn-type"
+#endif
+
+#include "gl_linked_list.h"
+
+#if SIGNAL_SAFE_LIST
+
+# if USE_ISOC_THREADS || USE_POSIX_THREADS || USE_ISOC_AND_POSIX_THREADS /* || USE_WINDOWS_THREADS */
+/* This test works only with POSIX compatible threads.
+   With Windows threads, send_signal() has to be implemented as
+     raise (SIGINT);
+   hence only test == 2 tests anything, and in fact only 5 signals arrive.
+   This small test is not able to detect a buggy implementation.  Therefore
+   mark the test as skipped in this case.  */
+
+#  include <signal.h>
+#  include <stdint.h>
+#  include <stdlib.h>
+#  include <unistd.h>
+#  include <time.h>
+
+#  include "glthread/thread.h"
+#  include "glthread/yield.h"
+
+#  include "macros.h"
+
+#  define RANDOM(n) (rand () % (n))
+#  define RANDOM_OBJECT() ((void *) (uintptr_t) RANDOM (10000))
+
+/* test == 1: signals are executed in an idle thread.
+   test == 2: signals are executed in the signal-sending thread.
+   test == 3: signals are executed in the mutator thread.  */
+static int volatile test;
+
+static uintptr_t volatile sum_before_current_operation;
+static uintptr_t volatile sum_after_current_operation;
+
+static gl_list_t volatile list1;
+
+static gl_thread_t volatile signal_target;
+
+/* Statistics.  */
+static unsigned int volatile num_mutations;
+static unsigned int volatile num_signals_sent;
+static unsigned int volatile num_signals_arrived;
+
+/* Blocks the SIGINT signal in the current thread.  */
+static void
+block_sigint (void)
+{
+  sigset_t mask;
+
+  sigemptyset (&mask);
+  sigaddset (&mask, SIGINT);
+  sigprocmask (SIG_BLOCK, &mask, NULL); /* equivalent to pthread_sigmask */
+}
+
+/* This thread is idle.  */
+static void *
+idle_thread (void *arg)
+{
+  for (;;)
+    gl_thread_yield ();
+
+  /*NOTREACHED*/
+}
+
+/* The signal handler iterates through the list and verifies that the sum of
+   all elements in the list is one of the two allowed values.  */
+static _GL_ASYNC_SAFE void
+sigint_handler (int signo)
+{
+  num_signals_arrived++;
+
+  uintptr_t sum = 0;
+  {
+    gl_list_iterator_t iter = gl_list_iterator (list1);
+    const void *elt;
+
+    while (gl_list_iterator_next (&iter, &elt, NULL))
+      sum += (uintptr_t) elt;
+    gl_list_iterator_free (&iter);
+  }
+  if (!(sum == sum_before_current_operation
+        || sum == sum_after_current_operation))
+    {
+      /* POSIX does not allow uses of stdio from within a signal handler, but
+         it should work here, because the rest of the program does not use
+         stdio.  */
+      fprintf (stderr, "sum = %lu, expected %lu or %lu\n",
+               (unsigned long) sum,
+               (unsigned long) sum_before_current_operation,
+               (unsigned long) sum_after_current_operation);
+      fflush (stderr);
+      abort ();
+    }
+}
+
+/* Sends a SIGINT signal to the current process.  */
+static void
+send_signal (void)
+{
+#if 0
+  /* This does not work for test != 2, because raise() sends the signal to the
+     current thread always, and if test != 2 the signal is eternally blocked
+     in the current thread; thus it will never get delivered.  */
+  raise (SIGINT);
+#else
+  /* This works: Either
+       kill (getpid (), SIGINT);
+     or
+       pthread_kill (signal_target, SIGINT);
+     The difference is that for kill(), the OS determines the (only) thread that
+     has not blocked the signal, whereas for pthread_kill() we have manually
+     determined this thread.  */
+  kill (getpid (), SIGINT);
+#endif
+}
+
+/* This thread permanently sends SIGINT signals.  */
+static void *
+signal_sending_thread (void *arg)
+{
+  if (test != 2)
+    block_sigint ();
+
+  int repeat;
+
+  for (repeat = 1000; repeat > 0; repeat--)
+    {
+      num_signals_sent++; send_signal ();
+      num_signals_sent++; send_signal ();
+      num_signals_sent++; send_signal ();
+      num_signals_sent++; send_signal ();
+      num_signals_sent++; send_signal ();
+      {
+        struct timespec ts;
+        ts.tv_sec = 0; ts.tv_nsec = 1000000;
+        nanosleep (&ts, NULL);
+      }
+      gl_thread_yield ();
+    }
+
+  printf ("Sent %u signals. Received %u signals. Done after %u mutations.\n",
+          num_signals_sent, num_signals_arrived, num_mutations);
+
+  exit (0);
+
+  /*NOTREACHED*/
+}
+
+/* This thread repeatedly adds and removes objects from the list.  */
+static void *
+mutator_thread (void *arg)
+{
+  if (test != 3)
+    block_sigint ();
+
+  gl_list_t list2 = (gl_list_t) arg;
+
+  for (num_mutations = 0; ; num_mutations++)
+    {
+      unsigned int operation = RANDOM (2);
+      switch (operation)
+        {
+        case 0: /* Add an element.  */
+          {
+            const void *obj = RANDOM_OBJECT ();
+            ASSERT (gl_list_nx_add_first (list2, obj) != NULL);
+            sum_after_current_operation =
+              sum_before_current_operation + (uintptr_t) obj;
+            ASSERT (gl_list_nx_add_first (list1, obj) != NULL);
+            sum_before_current_operation = sum_after_current_operation;
+          }
+          break;
+        case 1: /* Remove an element.  */
+          if (gl_list_size (list2) > 0)
+            {
+              size_t index = RANDOM (gl_list_size (list2));
+              const void *obj = gl_list_get_at (list2, index);
+              ASSERT (gl_list_remove (list2, obj));
+              sum_after_current_operation =
+                sum_before_current_operation - (uintptr_t) obj;
+              ASSERT (gl_list_remove (list1, obj));
+              sum_before_current_operation = sum_after_current_operation;
+            }
+          break;
+        }
+    }
+
+  /*NOTREACHED*/
+}
+
+int
+main (int argc, char *argv[])
+{
+  test = atoi (argv[1]);
+
+  /* Allow the user to provide a non-default random seed on the command line.  */
+  if (argc > 2)
+    srand (atoi (argv[2]));
+
+  gl_list_t list2;
+  /* Initialize list1 and list2.  */
+  {
+    size_t initial_size = RANDOM (50);
+    const void **contents =
+      (const void **) malloc (initial_size * sizeof (const void *));
+    size_t i;
+
+    for (i = 0; i < initial_size; i++)
+      contents[i] = RANDOM_OBJECT ();
+
+    list1 = gl_list_nx_create_empty (GL_LINKED_LIST, NULL, NULL, NULL, true);
+    ASSERT (list1 != NULL);
+    for (i = 0; i < initial_size; i++)
+      ASSERT (gl_list_nx_add_first (list1, contents[i]) != NULL);
+
+    list2 = gl_list_nx_create_empty (GL_LINKED_LIST, NULL, NULL, NULL, true);
+    ASSERT (list2 != NULL);
+    for (i = 0; i < initial_size; i++)
+      ASSERT (gl_list_nx_add_last (list2, contents[i]) != NULL);
+
+    uintptr_t initial_sum = 0;
+    for (i = 0; i < initial_size; i++)
+      initial_sum += (uintptr_t) contents[i];
+    sum_before_current_operation = initial_sum;
+    sum_after_current_operation = initial_sum;
+  }
+
+  /* Install the signal handler.
+     It needs to be done with sigaction(), not signal(), otherwise on Solaris
+     and AIX the program crashes at the second incoming SIGINT.  */
+  #if 0
+  signal (SIGINT, sigint_handler);
+  #else
+  {
+    struct sigaction action;
+    action.sa_handler = sigint_handler;
+    action.sa_flags = SA_RESTART | SA_NODEFER;
+    sigemptyset (&action.sa_mask);
+    ASSERT (sigaction (SIGINT, &action, NULL) == 0);
+  }
+  #endif
+
+  /* Launch the threads.  */
+  switch (test)
+    {
+    case 1:
+      {
+        signal_target = gl_thread_create (idle_thread, NULL);
+        gl_thread_create (mutator_thread, list2);
+        signal_sending_thread (NULL);
+        abort ();
+      }
+
+    case 2:
+      {
+        gl_thread_create (mutator_thread, list2);
+        signal_target = gl_thread_self (); signal_sending_thread (NULL);
+        abort ();
+      }
+
+    case 3:
+      {
+        signal_target = gl_thread_create (mutator_thread, list2);
+        signal_sending_thread (NULL);
+        abort ();
+      }
+
+    default:
+      ASSERT (false);
+    }
+}
+
+# else
+
+#  include <stdio.h>
+
+int
+main ()
+{
+  fputs ("Skipping test: POSIX compatible multithreading not enabled\n", stderr);
+  return 77;
+}
+
+# endif
+
+#else
+
+# include <stdio.h>
+
+int
+main ()
+{
+  fputs ("Skipping test: signal-safety of linked lists is not enabled\n", stderr);
+  return 77;
+}
+
+#endif

tests/test-asyncsafe-linked_list.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+
+st=0
+for i in 1 2 3 ; do
+  ${CHECKER} ./test-asyncsafe-linked_list${EXEEXT} $i
+  result=$?
+  if test $result = 77; then
+    st=77
+    break
+  fi
+  if test $result != 0; then
+    echo test-asyncsafe-linked_list.sh: test case $i failed >&2
+    st=1
+  fi
+done
+exit $st