MFC r314179 r314206 r314424

Add sem_clockwait_np()

This function allows the caller to specify the reference clock
and choose between absolute and relative mode.  In relative mode,
the remaining time can be returned.

The API is similar to clock_nanosleep(3).  Thanks to Ed Schouten
for that suggestion.

While I'm here, reduce the sleep time in the semaphore "child"
test to greatly reduce its runtime.  Also add a reasonable timeout.

Relnotes:	yes
Sponsored by:	Dell EMC

6 files changed, 97 insertions, 25 deletions

diff --git a/lib/libc/gen/Makefile.inc b/lib/libc/gen/Makefile.inc
index a75a0d1..f1d1378 100644
--- a/lib/libc/gen/Makefile.inc
+++ b/lib/libc/gen/Makefile.inc
@@ -461,6 +461,7 @@ MLINKS+=scandir.3 alphasort.3
 MLINKS+=sem_open.3 sem_close.3 \
 	sem_open.3 sem_unlink.3
 MLINKS+=sem_wait.3 sem_trywait.3
+MLINKS+=sem_timedwait.3 sem_clockwait_np.3
 MLINKS+=send.2 sendmmsg.2
 MLINKS+=setjmp.3 _longjmp.3 \
 	setjmp.3 _setjmp.3 \
diff --git a/lib/libc/gen/Symbol.map b/lib/libc/gen/Symbol.map
index 0d5dfec..f452297 100644
--- a/lib/libc/gen/Symbol.map
+++ b/lib/libc/gen/Symbol.map
@@ -418,6 +418,10 @@ FBSD_1.4 {
 	stravis;
 };
 
+FBSD_1.5 {
+	sem_clockwait_np;
+};
+
 FBSDprivate_1.0 {
 	/* needed by thread libraries */
 	__thr_jtable;
diff --git a/lib/libc/gen/sem_new.c b/lib/libc/gen/sem_new.c
index 8fe027f..d36d1e2 100644
--- a/lib/libc/gen/sem_new.c
+++ b/lib/libc/gen/sem_new.c
@@ -56,6 +56,7 @@ __weak_reference(_sem_init, sem_init);
 __weak_reference(_sem_open, sem_open);
 __weak_reference(_sem_post, sem_post);
 __weak_reference(_sem_timedwait, sem_timedwait);
+__weak_reference(_sem_clockwait_np, sem_clockwait_np);
 __weak_reference(_sem_trywait, sem_trywait);
 __weak_reference(_sem_unlink, sem_unlink);
 __weak_reference(_sem_wait, sem_wait);
@@ -345,23 +346,34 @@ usem_wake(struct _usem2 *sem)
 }
 
 static __inline int
-usem_wait(struct _usem2 *sem, const struct timespec *abstime)
+usem_wait(struct _usem2 *sem, clockid_t clock_id, int flags,
+    const struct timespec *rqtp, struct timespec *rmtp)
 {
-	struct _umtx_time *tm_p, timeout;
+	struct {
+		struct _umtx_time timeout;
+		struct timespec remain;
+	} tms;
+	void *tm_p;
 	size_t tm_size;
+	int retval;
 
-	if (abstime == NULL) {
+	if (rqtp == NULL) {
 		tm_p = NULL;
 		tm_size = 0;
 	} else {
-		timeout._clockid = CLOCK_REALTIME;
-		timeout._flags = UMTX_ABSTIME;
-		timeout._timeout = *abstime;
-		tm_p = &timeout;
-		tm_size = sizeof(timeout);
+		tms.timeout._clockid = clock_id;
+		tms.timeout._flags = (flags & TIMER_ABSTIME) ? UMTX_ABSTIME : 0;
+		tms.timeout._timeout = *rqtp;
+		tm_p = &tms;
+		tm_size = sizeof(tms);
 	}
-	return _umtx_op(sem, UMTX_OP_SEM2_WAIT, 0, 
-		    (void *)tm_size, __DECONST(void*, tm_p));
+	retval = _umtx_op(sem, UMTX_OP_SEM2_WAIT, 0, (void *)tm_size, tm_p);
+	if (retval == -1 && errno == EINTR && (flags & TIMER_ABSTIME) == 0 &&
+	    rqtp != NULL && rmtp != NULL) {
+		*rmtp = tms.remain;
+	}
+
+	return (retval);
 }
 
 int
@@ -381,8 +393,8 @@ _sem_trywait(sem_t *sem)
 }
 
 int
-_sem_timedwait(sem_t * __restrict sem,
-	const struct timespec * __restrict abstime)
+_sem_clockwait_np(sem_t * __restrict sem, clockid_t clock_id, int flags,
+	const struct timespec *rqtp, struct timespec *rmtp)
 {
 	int val, retval;
 
@@ -393,7 +405,8 @@ _sem_timedwait(sem_t * __restrict sem,
 	_pthread_testcancel();
 	for (;;) {
 		while (USEM_COUNT(val = sem->_kern._count) > 0) {
-			if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
+			if (atomic_cmpset_acq_int(&sem->_kern._count, val,
+			    val - 1))
 				return (0);
 		}
 
@@ -406,20 +419,28 @@ _sem_timedwait(sem_t * __restrict sem,
 		 * The timeout argument is only supposed to
 		 * be checked if the thread would have blocked.
 		 */
-		if (abstime != NULL) {
-			if (abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0) {
+		if (rqtp != NULL) {
+			if (rqtp->tv_nsec >= 1000000000 || rqtp->tv_nsec < 0) {
 				errno = EINVAL;
 				return (-1);
 			}
 		}
 		_pthread_cancel_enter(1);
-		retval = usem_wait(&sem->_kern, abstime);
+		retval = usem_wait(&sem->_kern, clock_id, flags, rqtp, rmtp);
 		_pthread_cancel_leave(0);
 	}
 	return (retval);
 }
 
 int
+_sem_timedwait(sem_t * __restrict sem,
+	const struct timespec * __restrict abstime)
+{
+	return (_sem_clockwait_np(sem, CLOCK_REALTIME, TIMER_ABSTIME, abstime,
+	    NULL));
+};
+
+int
 _sem_wait(sem_t *sem)
 {
 	return _sem_timedwait(sem, NULL);
diff --git a/lib/libc/gen/sem_timedwait.3 b/lib/libc/gen/sem_timedwait.3
index 254af60..1623ebe 100644
--- a/lib/libc/gen/sem_timedwait.3
+++ b/lib/libc/gen/sem_timedwait.3
@@ -34,18 +34,22 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd March 3, 2008
+.Dd March 10, 2017
 .Dt SEM_TIMEDWAIT 3
 .Os
 .Sh NAME
-.Nm sem_timedwait
+.Nm sem_timedwait ,
+.Nm sem_clockwait_np
 .Nd "lock a semaphore"
 .Sh LIBRARY
 .Lb libpthread
 .Sh SYNOPSIS
 .In semaphore.h
+.In time.h
 .Ft int
 .Fn sem_timedwait "sem_t *sem" "const struct timespec *abs_timeout"
+.Ft int
+.Fn sem_clockwait_np "sem_t * restrict sem" "clockid_t clock_id" "int flags" "const struct timespec * rqtp" "struct timespec * rmtp"
 .Sh DESCRIPTION
 The
 .Fn sem_timedwait
@@ -77,10 +81,40 @@ clock.
 The validity of the
 .Fa abs_timeout
 is not checked if the semaphore can be locked immediately.
-.Sh RETURN VALUES
+.Pp
 The
-.Fn sem_timedwait
-function returns zero if the calling process successfully performed the
+.Fn sem_clockwait_np
+function is a more flexible variant of
+.Fn sem_timedwait .
+The
+.Fa clock_id
+parameter specifies the reference clock.
+If the
+.Fa flags
+parameter contains
+.Dv TIMER_ABSTIME ,
+then the requested timeout
+.Pq Fa rqtp
+is an absolute timeout; otherwise,
+the timeout is relative.
+If this function fails with
+.Er EINTR
+and the timeout is relative,
+a non-NULL
+.Fa rmtp
+will be updated to contain the amount of time remaining in the interval
+.Po
+the requested time minus the time actually slept
+.Pc .
+An absolute timeout has no effect on
+.Fa rmtp .
+A single structure can be used for both
+.Fa rqtp
+and
+.Fa rmtp .
+.Sh RETURN VALUES
+These
+functions return zero if the calling process successfully performed the
 semaphore lock operation on the semaphore designated by
 .Fa sem .
 If the call was unsuccessful, the state of the semaphore is unchanged,
@@ -88,9 +122,7 @@ and the function returns a value of \-1 and sets the global variable
 .Va errno
 to indicate the error.
 .Sh ERRORS
-The
-.Fn sem_timedwait
-function will fail if:
+These functions will fail if:
 .Bl -tag -width Er
 .It Bq Er EINVAL
 The
@@ -114,6 +146,18 @@ The
 .Fn sem_timedwait
 function conforms to
 .St -p1003.1-2004 .
+The
+.Fn sem_clockwait_np
+function is not specified by any standard;
+it exists only on
+.Fx
+at the time of this writing.
 .Sh HISTORY
-The function first appeared in
+The
+.Fn sem_timedwait
+function first appeared in
 .Fx 5.0 .
+The
+.Fn sem_clockwait_np
+function first appeared in
+.Fx 12.0 .
diff --git a/lib/libc/include/namespace.h b/lib/libc/include/namespace.h
index c95829e..52e9b25 100644
--- a/lib/libc/include/namespace.h
+++ b/lib/libc/include/namespace.h
@@ -217,6 +217,7 @@
 #define		sem_open			_sem_open
 #define		sem_post			_sem_post
 #define		sem_timedwait			_sem_timedwait
+#define		sem_clockwait_np		_sem_clockwait_np
 #define		sem_trywait			_sem_trywait
 #define		sem_unlink			_sem_unlink
 #define		sem_wait			_sem_wait
diff --git a/lib/libc/include/un-namespace.h b/lib/libc/include/un-namespace.h
index 0233348..e40e6fd 100644
--- a/lib/libc/include/un-namespace.h
+++ b/lib/libc/include/un-namespace.h
@@ -198,6 +198,7 @@
 #undef		sem_open
 #undef		sem_post
 #undef		sem_timedwait
+#undef		sem_clockwait_np
 #undef		sem_trywait
 #undef		sem_unlink
 #undef		sem_wait