nptl: Return EINVAL for pthread_mutex_clocklock/PI with CLOCK_MONOTONIC [BZ #26801]

Linux futex FUTEX_LOCK_PI operation only supports CLOCK_REALTIME,
so pthread_mutex_clocklock operation with priority aware mutexes
may fail depending of the input timeout.

Also, it is not possible to convert a CLOCK_MONOTONIC to a
CLOCK_REALTIME due the possible wall clock time change which might
invalid the requested timeout.

Checked on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Lukasz Majewski <lukma@denx.de>

nptl/Makefile

@@ -265,7 +265,7 @@ tests = tst-attr2 tst-attr3 tst-default-attr \
 	tst-mutex5a tst-mutex7a \
 	tst-mutexpi1 tst-mutexpi2 tst-mutexpi3 tst-mutexpi4 \
 	tst-mutexpi5 tst-mutexpi5a tst-mutexpi6 tst-mutexpi7 tst-mutexpi7a \
-	tst-mutexpi9 \
+	tst-mutexpi9 tst-mutexpi10 \
 	tst-cond22 tst-cond26 \
 	tst-robustpi1 tst-robustpi2 tst-robustpi3 tst-robustpi4 tst-robustpi5 \
 	tst-robustpi6 tst-robustpi7 tst-robustpi9 \

nptl/pthread_mutex_timedlock.c

@@ -313,6 +313,13 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex,
     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
       {
+	/* Currently futex FUTEX_LOCK_PI operation only provides support for
+	   CLOCK_REALTIME and trying to emulate by converting a
+	   CLOCK_MONOTONIC to CLOCK_REALTIME will take in account possible
+	   changes to the wall clock.  */
+	if (__glibc_unlikely (clockid != CLOCK_REALTIME))
+	  return EINVAL;
+
 	int kind, robust;
 	{
 	  /* See concurrency notes regarding __kind in struct __pthread_mutex_s

nptl/tst-mutexpi10.c

@@ -0,0 +1,68 @@
+/* Check if pthread_mutex_clocklock with PRIO_INHERIT fails with clock
+   different than CLOCK_REALTIME.
+   Copyright (C) 2020 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 <pthread.h>
+#include <errno.h>
+#include <array_length.h>
+
+#include <support/check.h>
+#include <support/xthread.h>
+#include <support/timespec.h>
+
+static int
+do_test (void)
+{
+  const int types[] = {
+    PTHREAD_MUTEX_NORMAL,
+    PTHREAD_MUTEX_ERRORCHECK,
+    PTHREAD_MUTEX_RECURSIVE,
+    PTHREAD_MUTEX_ADAPTIVE_NP
+  };
+  const int robust[] = {
+    PTHREAD_MUTEX_STALLED,
+    PTHREAD_MUTEX_ROBUST
+  };
+
+
+  for (int t = 0; t < array_length (types); t++)
+    for (int r = 0; r < array_length (robust); r++)
+      {
+	pthread_mutexattr_t attr;
+
+	xpthread_mutexattr_init (&attr);
+	xpthread_mutexattr_setprotocol (&attr, PTHREAD_PRIO_INHERIT);
+	xpthread_mutexattr_settype (&attr, types[t]);
+	xpthread_mutexattr_setrobust (&attr, robust[r]);
+
+	pthread_mutex_t mtx;
+	xpthread_mutex_init (&mtx, &attr);
+
+	struct timespec tmo = timespec_add (xclock_now (CLOCK_MONOTONIC),
+					    make_timespec (0, 100000000));
+
+	TEST_COMPARE (pthread_mutex_clocklock (&mtx, CLOCK_MONOTONIC, &tmo),
+		      EINVAL);
+
+	xpthread_mutex_destroy (&mtx);
+      }
+
+  return 0;
+}
+
+#include <support/test-driver.c>

sysdeps/pthread/tst-mutex5.c

@@ -112,7 +112,9 @@ static int do_test (void)
 {
   do_test_clock (CLOCK_USE_TIMEDLOCK, "timedlock");
   do_test_clock (CLOCK_REALTIME, "clocklock(realtime)");
+#ifndef ENABLE_PI
   do_test_clock (CLOCK_MONOTONIC, "clocklock(monotonic)");
+#endif
   return 0;
 }
 

sysdeps/pthread/tst-mutex9.c

@@ -133,7 +133,9 @@ do_test (void)
 {
   do_test_clock (CLOCK_USE_TIMEDLOCK);
   do_test_clock (CLOCK_REALTIME);
+#ifndef ENABLE_PI
   do_test_clock (CLOCK_MONOTONIC);
+#endif
   return 0;
 }