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[RFC] Add pthread_cond_timedwaitonclock_np


C++11's std::condition_variable::wait_until specifies the clock to be
used at the time of the wait and permits separate waits on the same
instance using different clocks.

Unfortunately pthread_cond_timedwait always uses the clock that was
specified (or defaulted) when pthread_cond_init was called. libstdc++'s
current implementation converts all waits to
std::chrono::system_clock (i.e. CLOCK_REALTIME) which can race against
the system clock changing.

Inventing a brand-new function pthread_cond_timedwaitonclock_np which
accepts both the clock and the time point as parameters is
straightforward and means that the C++11 standard behaviour can be
implemented in libstdc++ on Linux at least.

(This patch is only to the C implementation of pthread_cond_timedwait so
it is necessary to remove pthread_cond_timedwait.S and
pthread_cond_wait.S to use it on x86 and x86_64 at the moment. If the
approach is deemed acceptable I'll work on fixing those too along with
the documentation.)

Signed-off-by: Mike Crowe <mac@mcrowe.com>
---
 conform/data/pthread.h-data   |   3 +
 nptl/Makefile                 |   4 +-
 nptl/Versions                 |   1 +
 nptl/pthread_cond_timedwait.c |  26 ++++--
 nptl/tst-cond11-onclock.c     | 206 ++++++++++++++++++++++++++++++++++++++++++
 nptl/tst-cond5-onclock.c      | 113 +++++++++++++++++++++++
 sysdeps/nptl/pthread.h        |  13 +++
 7 files changed, 356 insertions(+), 10 deletions(-)
 create mode 100644 nptl/tst-cond11-onclock.c
 create mode 100644 nptl/tst-cond5-onclock.c

diff --git a/conform/data/pthread.h-data b/conform/data/pthread.h-data
index c1e32c8..d52f298 100644
--- a/conform/data/pthread.h-data
+++ b/conform/data/pthread.h-data
@@ -92,6 +92,9 @@ function int pthread_cond_destroy (pthread_cond_t*)
 function int pthread_cond_init (pthread_cond_t*, const pthread_condattr_t*)
 function int pthread_cond_signal (pthread_cond_t*)
 function int pthread_cond_timedwait (pthread_cond_t*, pthread_mutex_t*, const struct timespec*)
+#if !defined POSIX && !defined UNIX98 && !defined XOPEN2K
+function int pthread_cond_timedwaitonclock_np (pthread_cond_t*, pthread_mutex_t*, clockid_t, const struct timespec*)
+#endif
 function int pthread_cond_wait (pthread_cond_t*, pthread_mutex_t*)
 function int pthread_condattr_destroy (pthread_condattr_t*)
 #if !defined POSIX && !defined UNIX98 && !defined XOPEN2K
diff --git a/nptl/Makefile b/nptl/Makefile
index 4544aa2..ff06939 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -221,8 +221,8 @@ tests = tst-typesizes \
 	tst-mutexpi5a tst-mutexpi6 tst-mutexpi7 tst-mutexpi7a tst-mutexpi8 \
 	tst-mutexpi9 \
 	tst-spin1 tst-spin2 tst-spin3 tst-spin4 \
-	tst-cond1 tst-cond2 tst-cond3 tst-cond4 tst-cond5 tst-cond6 tst-cond7 \
-	tst-cond8 tst-cond9 tst-cond10 tst-cond11 tst-cond12 tst-cond13 \
+	tst-cond1 tst-cond2 tst-cond3 tst-cond4 tst-cond5 tst-cond5-onclock tst-cond6 tst-cond7 \
+	tst-cond8 tst-cond9 tst-cond10 tst-cond11 tst-cond11-onclock tst-cond12 tst-cond13 \
 	tst-cond14 tst-cond15 tst-cond16 tst-cond17 tst-cond18 tst-cond19 \
 	tst-cond20 tst-cond21 tst-cond22 tst-cond23 tst-cond24 tst-cond25 \
 	tst-cond-except \
diff --git a/nptl/Versions b/nptl/Versions
index 34e4b46..476301f 100644
--- a/nptl/Versions
+++ b/nptl/Versions
@@ -267,6 +267,7 @@ libpthread {
   }
 
   GLIBC_2.22 {
+    pthread_cond_timedwaitonclock_np;
   }
 
   GLIBC_PRIVATE {
diff --git a/nptl/pthread_cond_timedwait.c b/nptl/pthread_cond_timedwait.c
index 10b0a61..a4c0ee3 100644
--- a/nptl/pthread_cond_timedwait.c
+++ b/nptl/pthread_cond_timedwait.c
@@ -49,8 +49,9 @@ struct _condvar_cleanup_buffer
 };
 
 int
-__pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
-			  const struct timespec *abstime)
+pthread_cond_timedwaitonclock_np (pthread_cond_t *cond, pthread_mutex_t *mutex,
+				  clockid_t clockid,
+				  const struct timespec *abstime)
 {
   struct _pthread_cleanup_buffer buffer;
   struct _condvar_cleanup_buffer cbuffer;
@@ -120,8 +121,7 @@ __pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
 # ifdef __NR_clock_gettime
 	INTERNAL_SYSCALL_DECL (err);
 	(void) INTERNAL_VSYSCALL (clock_gettime, err, 2,
-				  (cond->__data.__nwaiters
-				   & ((1 << COND_NWAITERS_SHIFT) - 1)),
+				  clockid,
 				  &rt);
 	/* Convert the absolute timeout value to a relative timeout.  */
 	rt.tv_sec = abstime->tv_sec - rt.tv_sec;
@@ -175,8 +175,7 @@ __pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
 
       if (pi_flag)
 	{
-	  unsigned int clockbit = (cond->__data.__nwaiters & 1
-				   ? 0 : FUTEX_CLOCK_REALTIME);
+	  unsigned int clockbit = clockid ? 0 : FUTEX_CLOCK_REALTIME;
 	  err = lll_futex_timed_wait_requeue_pi (&cond->__data.__futex,
 						 futex_val, abstime, clockbit,
 						 &mutex->__data.__lock,
@@ -193,8 +192,7 @@ __pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
 	  err = lll_futex_timed_wait (&cond->__data.__futex,
 				      futex_val, &rt, pshared);
 #else
-	  unsigned int clockbit = (cond->__data.__nwaiters & 1
-				   ? 0 : FUTEX_CLOCK_REALTIME);
+	  unsigned int clockbit = clockid ? 0 : FUTEX_CLOCK_REALTIME;
 	  err = lll_futex_timed_wait_bitset (&cond->__data.__futex, futex_val,
 					     abstime, clockbit, pshared);
 #endif
@@ -264,5 +262,17 @@ __pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
   return err ?: result;
 }
 
+int
+__pthread_cond_timedwait (cond, mutex, abstime)
+     pthread_cond_t *cond;
+     pthread_mutex_t *mutex;
+     const struct timespec *abstime;
+{
+    return pthread_cond_timedwaitonclock_np (cond, mutex,
+					     (cond->__data.__nwaiters
+					      & ((1 << COND_NWAITERS_SHIFT) - 1)),
+					     abstime);
+}
+
 versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
 		  GLIBC_2_3_2);
diff --git a/nptl/tst-cond11-onclock.c b/nptl/tst-cond11-onclock.c
new file mode 100644
index 0000000..15b3730
--- /dev/null
+++ b/nptl/tst-cond11-onclock.c
@@ -0,0 +1,206 @@
+/* Copyright (C) 2003-2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
+
+   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 <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <time.h>
+#include <unistd.h>
+
+
+#if defined _POSIX_CLOCK_SELECTION && _POSIX_CLOCK_SELECTION >= 0
+static int
+run_test (clockid_t attr_clock, clockid_t wait_clock)
+{
+  pthread_condattr_t condattr;
+  pthread_cond_t cond;
+  pthread_mutexattr_t mutattr;
+  pthread_mutex_t mut;
+
+  printf ("attr_clock = %d, wait_clock = %d\n", (int) attr_clock, (int) wait_clock);
+
+  if (pthread_condattr_init (&condattr) != 0)
+    {
+      puts ("condattr_init failed");
+      return 1;
+    }
+
+  if (pthread_condattr_setclock (&condattr, attr_clock) != 0)
+    {
+      puts ("condattr_setclock failed");
+      return 1;
+    }
+
+  clockid_t cl2;
+  if (pthread_condattr_getclock (&condattr, &cl2) != 0)
+    {
+      puts ("condattr_getclock failed");
+      return 1;
+    }
+  if (attr_clock != cl2)
+    {
+      printf ("condattr_getclock returned wrong value: %d, expected %d\n",
+	      (int) cl2, (int) attr_clock);
+      return 1;
+    }
+
+  if (pthread_cond_init (&cond, &condattr) != 0)
+    {
+      puts ("cond_init failed");
+      return 1;
+    }
+
+  if (pthread_condattr_destroy (&condattr) != 0)
+    {
+      puts ("condattr_destroy failed");
+      return 1;
+    }
+
+  if (pthread_mutexattr_init (&mutattr) != 0)
+    {
+      puts ("mutexattr_init failed");
+      return 1;
+    }
+
+  if (pthread_mutexattr_settype (&mutattr, PTHREAD_MUTEX_ERRORCHECK) != 0)
+    {
+      puts ("mutexattr_settype failed");
+      return 1;
+    }
+
+  if (pthread_mutex_init (&mut, &mutattr) != 0)
+    {
+      puts ("mutex_init failed");
+      return 1;
+    }
+
+  if (pthread_mutexattr_destroy (&mutattr) != 0)
+    {
+      puts ("mutexattr_destroy failed");
+      return 1;
+    }
+
+  if (pthread_mutex_lock (&mut) != 0)
+    {
+      puts ("mutex_lock failed");
+      return 1;
+    }
+
+  if (pthread_mutex_lock (&mut) != EDEADLK)
+    {
+      puts ("2nd mutex_lock did not return EDEADLK");
+      return 1;
+    }
+
+  struct timespec ts;
+  if (clock_gettime (wait_clock, &ts) != 0)
+    {
+      puts ("clock_gettime failed");
+      return 1;
+    }
+
+  /* Wait one second.  */
+  ++ts.tv_sec;
+
+  int e = pthread_cond_timedwaitonclock_np (&cond, &mut, wait_clock, &ts);
+  if (e == 0)
+    {
+      puts ("cond_timedwait succeeded");
+      return 1;
+    }
+  else if (e != ETIMEDOUT)
+    {
+      puts ("cond_timedwait did not return ETIMEDOUT");
+      return 1;
+    }
+
+  struct timespec ts2;
+  if (clock_gettime (wait_clock, &ts2) != 0)
+    {
+      puts ("second clock_gettime failed");
+      return 1;
+    }
+
+  if (ts2.tv_sec < ts.tv_sec
+      || (ts2.tv_sec == ts.tv_sec && ts2.tv_nsec < ts.tv_nsec))
+    {
+      puts ("timeout too short");
+      return 1;
+    }
+
+  if (pthread_mutex_unlock (&mut) != 0)
+    {
+      puts ("mutex_unlock failed");
+      return 1;
+    }
+
+  if (pthread_mutex_destroy (&mut) != 0)
+    {
+      puts ("mutex_destroy failed");
+      return 1;
+    }
+
+  if (pthread_cond_destroy (&cond) != 0)
+    {
+      puts ("cond_destroy failed");
+      return 1;
+    }
+
+  return 0;
+}
+#endif
+
+
+static int
+do_test (void)
+{
+#if !defined _POSIX_CLOCK_SELECTION || _POSIX_CLOCK_SELECTION == -1
+
+  puts ("_POSIX_CLOCK_SELECTION not supported, test skipped");
+  return 0;
+
+#else
+
+  int res = run_test (CLOCK_REALTIME, CLOCK_REALTIME);
+
+# if defined _POSIX_MONOTONIC_CLOCK && _POSIX_MONOTONIC_CLOCK >= 0
+#  if _POSIX_MONOTONIC_CLOCK == 0
+  int e = sysconf (_SC_MONOTONIC_CLOCK);
+  if (e < 0)
+    puts ("CLOCK_MONOTONIC not supported");
+  else if (e == 0)
+    {
+      puts ("sysconf (_SC_MONOTONIC_CLOCK) must not return 0");
+      res = 1;
+    }
+  else
+#  endif
+    res |= run_test (CLOCK_REALTIME, CLOCK_MONOTONIC);
+    res |= run_test (CLOCK_MONOTONIC, CLOCK_MONOTONIC);
+    res |= run_test (CLOCK_MONOTONIC, CLOCK_REALTIME);
+# else
+  puts ("_POSIX_MONOTONIC_CLOCK not defined");
+# endif
+
+  return res;
+#endif
+}
+
+#define TIMEOUT 12
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/nptl/tst-cond5-onclock.c b/nptl/tst-cond5-onclock.c
new file mode 100644
index 0000000..ddb0ad1
--- /dev/null
+++ b/nptl/tst-cond5-onclock.c
@@ -0,0 +1,113 @@
+/* Copyright (C) 2002-2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
+
+   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 <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <sys/time.h>
+
+
+static pthread_mutex_t mut;
+static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
+
+
+static int
+do_test_onclock(clockid_t clockid)
+{
+  pthread_mutexattr_t ma;
+  int err;
+  struct timespec ts;
+
+  if (pthread_mutexattr_init (&ma) != 0)
+    {
+      puts ("mutexattr_init failed");
+      exit (1);
+    }
+
+  if (pthread_mutexattr_settype (&ma, PTHREAD_MUTEX_ERRORCHECK) != 0)
+    {
+      puts ("mutexattr_settype failed");
+      exit (1);
+    }
+
+  if (pthread_mutex_init (&mut, &ma) != 0)
+    {
+      puts ("mutex_init failed");
+      exit (1);
+    }
+
+  /* Get the mutex.  */
+  if (pthread_mutex_lock (&mut) != 0)
+    {
+      puts ("mutex_lock failed");
+      exit (1);
+    }
+
+  /* Waiting for the condition will fail.  But we want the timeout here.  */
+  if (clock_gettime (clockid, &ts) != 0)
+    {
+      puts ("clock_gettime failed");
+      exit (1);
+    }
+
+  ts.tv_nsec += 500000000;
+  if (ts.tv_nsec >= 1000000000)
+    {
+      ts.tv_nsec -= 1000000000;
+      ++ts.tv_sec;
+    }
+  err = pthread_cond_timedwaitonclock_np (&cond, &mut, clockid, &ts);
+  if (err == 0)
+    {
+      /* This could in theory happen but here without any signal and
+	 additional waiter it should not.  */
+      puts ("cond_timedwait succeeded");
+      exit (1);
+    }
+  else if (err != ETIMEDOUT)
+    {
+      printf ("cond_timedwait returned with %s\n", strerror (err));
+      exit (1);
+    }
+
+  err = pthread_mutex_unlock (&mut);
+  if (err != 0)
+    {
+      printf ("mutex_unlock failed: %s\n", strerror (err));
+      exit (1);
+    }
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  int rc;
+  rc = do_test_onclock(CLOCK_MONOTONIC);
+  if (rc == 0)
+    rc = do_test_onclock(CLOCK_REALTIME);
+
+  return rc;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/sysdeps/nptl/pthread.h b/sysdeps/nptl/pthread.h
index 89d0882..221924b 100644
--- a/sysdeps/nptl/pthread.h
+++ b/sysdeps/nptl/pthread.h
@@ -1002,6 +1002,19 @@ extern int pthread_cond_timedwait (pthread_cond_t *__restrict __cond,
 				   const struct timespec *__restrict __abstime)
      __nonnull ((1, 2, 3));
 
+/* Wait for condition variable COND to be signaled or broadcast until
+   ABSTIME measured by the specified clock. MUTEX is assumed to be
+   locked before. CLOCK is a clock specified. ABSTIME is an absolute
+   time specification against CLOCK's epoch.
+
+   This function is a cancellation point and therefore not marked with
+   __THROW. */
+extern int pthread_cond_timedwaitonclock_np (pthread_cond_t *__restrict __cond,
+					     pthread_mutex_t *__restrict __mutex,
+					     __clockid_t __clock_id,
+					     const struct timespec *__restrict __abstime)
+     __nonnull ((1, 2, 4));
+
 /* Functions for handling condition variable attributes.  */
 
 /* Initialize condition variable attribute ATTR.  */
-- 
2.1.4


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