diff mbox series

[2/2] nptl: Return ENOTSUP for pthread_mutex_clocklock/PI with CLOCK_MONOTONIC [BZ #26801]

Message ID 20201029194208.2715606-2-adhemerval.zanella@linaro.org
State Superseded
Headers
Series [1/2] nptl: Replace futex_lock_pi with __futex_lock_pi64 |

Commit Message

Adhemerval Zanella Oct. 29, 2020, 7:42 p.m. UTC 
  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.
---
 nptl/Makefile                  |  2 +-
 nptl/pthread_mutex_timedlock.c |  7 ++++
 nptl/tst-mutexpi10.c           | 68 ++++++++++++++++++++++++++++++++++
 sysdeps/pthread/tst-mutex5.c   |  2 +
 sysdeps/pthread/tst-mutex9.c   |  2 +
 5 files changed, 80 insertions(+), 1 deletion(-)
 create mode 100644 nptl/tst-mutexpi10.c

Comments

Florian Weimer Oct. 29, 2020, 8:26 p.m. UTC | #1 
* Adhemerval Zanella via Libc-alpha:

> diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
> index d839e6862f..923be4f734 100644
> --- a/nptl/pthread_mutex_timedlock.c
> +++ b/nptl/pthread_mutex_timedlock.c
> @@ -315,6 +315,13 @@ __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 ENOTSUP;
> +
>  	int kind, robust;
>  	{
>  	  /* See concurrency notes regarding __kind in struct __pthread_mutex_s

Do we know yet if the POSIX interfaces will be specified with EINVAL or
ENOTSUP for this error condition?

Thanks,
Florian
Adhemerval Zanella Oct. 30, 2020, 11:36 a.m. UTC | #2 
On 29/10/2020 17:26, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:
> 
>> diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
>> index d839e6862f..923be4f734 100644
>> --- a/nptl/pthread_mutex_timedlock.c
>> +++ b/nptl/pthread_mutex_timedlock.c
>> @@ -315,6 +315,13 @@ __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 ENOTSUP;
>> +
>>  	int kind, robust;
>>  	{
>>  	  /* See concurrency notes regarding __kind in struct __pthread_mutex_s
> 
> Do we know yet if the POSIX interfaces will be specified with EINVAL or
> ENOTSUP for this error condition?

I am not sure.  ENOTSUP seems slight better because it is what pthread_mutex_init 
returns in the case of prio_inherit_missing.
diff mbox series

Patch

diff --git a/nptl/Makefile b/nptl/Makefile
index d47e8a81d9..1ca0ec3950 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -266,7 +266,7 @@  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 \
diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
index d839e6862f..923be4f734 100644
--- a/nptl/pthread_mutex_timedlock.c
+++ b/nptl/pthread_mutex_timedlock.c
@@ -315,6 +315,13 @@  __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 ENOTSUP;
+
 	int kind, robust;
 	{
 	  /* See concurrency notes regarding __kind in struct __pthread_mutex_s
diff --git a/nptl/tst-mutexpi10.c b/nptl/tst-mutexpi10.c
new file mode 100644
index 0000000000..409ec97d47
--- /dev/null
+++ b/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) 2015-2020 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),
+		      ENOTSUP);
+
+	xpthread_mutex_destroy (&mtx);
+      }
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/pthread/tst-mutex5.c b/sysdeps/pthread/tst-mutex5.c
index 14490768c3..bfe1a79fa4 100644
--- a/sysdeps/pthread/tst-mutex5.c
+++ b/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;
 }
 
diff --git a/sysdeps/pthread/tst-mutex9.c b/sysdeps/pthread/tst-mutex9.c
index 2d7927b7c2..bfc01f8c75 100644
--- a/sysdeps/pthread/tst-mutex9.c
+++ b/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;
 }