Unlock mutex before going back to waiting for PI mutexes

[BZ #14417]
A futex call with FUTEX_WAIT_REQUEUE_PI returns with the mutex locked
on success.  If such a successful thread is pipped to the cond_lock by
another spuriously woken waiter, it could be sent back to wait on the
futex with the mutex lock held, thus causing a deadlock.  So it is
necessary that the thread relinquishes the mutex before going back to
sleep.

1 files changed, 249 insertions, 0 deletions

diff --git a/nptl/tst-cond24.c b/nptl/tst-cond24.c
new file mode 100644
index 0000000000..2eb2df1a3f
--- /dev/null
+++ b/nptl/tst-cond24.c
@@ -0,0 +1,249 @@
+/* Verify that condition variables synchronized by PI mutexes don't hang.
+   Copyright (C) 2012 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/>.  */
+
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <sys/time.h>
+#include <time.h>
+
+#define THREADS_NUM 5
+#define MAXITER 50000
+
+static pthread_mutex_t mutex;
+static pthread_mutexattr_t mutex_attr;
+static pthread_cond_t cond;
+static pthread_t threads[THREADS_NUM];
+static int pending = 0;
+
+typedef void * (*threadfunc) (void *);
+
+void *
+thread_fun_timed (void *arg)
+{
+  int *ret = arg;
+  int rv, i;
+
+  printf ("Started thread_fun_timed[%d]\n", *ret);
+
+  for (i = 0; i < MAXITER / THREADS_NUM; i++)
+    {
+      rv = pthread_mutex_lock (&mutex);
+      if (rv)
+        {
+	  printf ("pthread_mutex_lock: %s(%d)\n", strerror (rv), rv);
+	  *ret = 1;
+	  goto out;
+	}
+
+      while (!pending)
+	{
+	  struct timespec ts;
+	  clock_gettime(CLOCK_REALTIME, &ts);
+	  ts.tv_sec += 20;
+	  rv = pthread_cond_timedwait (&cond, &mutex, &ts);
+
+	  /* There should be no timeout either.  */
+	  if (rv)
+            {
+	      printf ("pthread_cond_wait: %s(%d)\n", strerror (rv), rv);
+	      *ret = 1;
+	      goto out;
+	    }
+	}
+
+      pending--;
+
+      rv = pthread_mutex_unlock (&mutex);
+      if (rv)
+        {
+	  printf ("pthread_mutex_unlock: %s(%d)\n", strerror (rv), rv);
+	  *ret = 1;
+	  goto out;
+	}
+    }
+
+  *ret = 0;
+
+out:
+  return ret;
+}
+
+void *
+thread_fun (void *arg)
+{
+  int *ret = arg;
+  int rv, i;
+
+  printf ("Started thread_fun[%d]\n", *ret);
+
+  for (i = 0; i < MAXITER / THREADS_NUM; i++)
+    {
+      rv = pthread_mutex_lock (&mutex);
+      if (rv)
+        {
+	  printf ("pthread_mutex_lock: %s(%d)\n", strerror (rv), rv);
+	  *ret = 1;
+	  goto out;
+	}
+
+      while (!pending)
+	{
+	  rv = pthread_cond_wait (&cond, &mutex);
+
+	  if (rv)
+            {
+	      printf ("pthread_cond_wait: %s(%d)\n", strerror (rv), rv);
+	      *ret = 1;
+	      goto out;
+	    }
+	}
+
+      pending--;
+
+      rv = pthread_mutex_unlock (&mutex);
+      if (rv)
+        {
+	  printf ("pthread_mutex_unlock: %s(%d)\n", strerror (rv), rv);
+	  *ret = 1;
+	  goto out;
+	}
+    }
+
+  *ret = 0;
+
+out:
+  return ret;
+}
+
+static int
+do_test_wait (threadfunc f)
+{
+  int i;
+  int rv;
+  int counter = 0;
+  int retval[THREADS_NUM];
+
+  puts ("Starting test");
+
+  rv = pthread_mutexattr_init (&mutex_attr);
+  if (rv)
+    {
+      printf ("pthread_mutexattr_init: %s(%d)\n", strerror (rv), rv);
+      return 1;
+    }
+
+  rv = pthread_mutexattr_setprotocol (&mutex_attr, PTHREAD_PRIO_INHERIT);
+  if (rv)
+    {
+      printf ("pthread_mutexattr_setprotocol: %s(%d)\n", strerror (rv), rv);
+      return 1;
+    }
+
+  rv = pthread_mutex_init (&mutex, &mutex_attr);
+  if (rv)
+    {
+      printf ("pthread_mutex_init: %s(%d)\n", strerror (rv), rv);
+      return 1;
+    }
+
+  rv = pthread_cond_init (&cond, NULL);
+  if (rv)
+    {
+      printf ("pthread_cond_init: %s(%d)\n", strerror (rv), rv);
+      return 1;
+    }
+
+  for (i = 0; i < THREADS_NUM; i++)
+    {
+      retval[i] = i;
+      rv = pthread_create (&threads[i], NULL, f, &retval[i]);
+      if (rv)
+        {
+          printf ("pthread_create: %s(%d)\n", strerror (rv), rv);
+          return 1;
+        }
+    }
+
+  for (; counter < MAXITER; counter++)
+    {
+      rv = pthread_mutex_lock (&mutex);
+      if (rv)
+        {
+          printf ("pthread_mutex_lock: %s(%d)\n", strerror (rv), rv);
+          return 1;
+        }
+
+      if (!(counter % 100))
+	printf ("counter: %d\n", counter);
+      pending += 1;
+
+      rv = pthread_cond_signal (&cond);
+      if (rv)
+        {
+          printf ("pthread_cond_signal: %s(%d)\n", strerror (rv), rv);
+          return 1;
+        }
+
+      rv = pthread_mutex_unlock (&mutex);
+      if (rv)
+        {
+          printf ("pthread_mutex_unlock: %s(%d)\n", strerror (rv), rv);
+          return 1;
+        }
+    }
+
+  for (i = 0; i < THREADS_NUM; i++)
+    {
+      void *ret;
+      rv = pthread_join (threads[i], &ret);
+      if (rv)
+        {
+          printf ("pthread_join: %s(%d)\n", strerror (rv), rv);
+          return 1;
+        }
+      if (ret && *(int *)ret)
+        {
+	  printf ("Thread %d returned with an error\n", i);
+	  return 1;
+	}
+    }
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  puts ("Testing pthread_cond_wait");
+  int ret = do_test_wait (thread_fun);
+  if (ret)
+    return ret;
+
+  puts ("Testing pthread_cond_timedwait");
+  return do_test_wait (thread_fun_timed);
+}
+
+#define TIMEOUT 10
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"