[PATCH 2/8] additions to src/time

[Jens Gustedt <Jens.Gustedt@inria.fr>]

This adds two functions, thrd_sleep and timespec_get. Both have easy
functional equivalences in POSIX, but these have subtle differences in
the handling of errors.

thrd_sleep forces concrete numerical values as error return

timespec_get has a call interface that is incompatible with POSIX because
it has a bogus coding for its clock constants, and also this clock
constants must be returned in case of success. For the moment we only
implement one single clock, TIME_UTC, and map this to
CLOCK_REALTIME. This is the clock that we later need to measure time for
the timedlock and timedwait.

Also, other than for clock_gettime, C doesn't specify touching errno for
timespec_get. Because CLOCK_REALTIME can be obtained very efficiently
through VDSO and messing with errno is clearly the wrong step to go, we
try to avoid this.
---
 src/time/thrd_sleep.c   |   26 ++++++++++++++++++++++++++
 src/time/timespec_get.c |   31 +++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 src/time/thrd_sleep.c
 create mode 100644 src/time/timespec_get.c

diff --git a/src/time/thrd_sleep.c b/src/time/thrd_sleep.c
new file mode 100644
index 0000000..3dbfe47
--- /dev/null
+++ b/src/time/thrd_sleep.c
@@ -0,0 +1,26 @@
+#include <time.h>
+#include <errno.h>
+#include "syscall.h"
+#include "libc.h"
+#include "threads.h"
+
+/* Roughly __syscall already returns the right thing: 0 if all went
+   well or a negative error indication, otherwise. */
+int thrd_sleep(const struct timespec *req, struct timespec *rem)
+{
+	int ret = __syscall(SYS_nanosleep, req, rem);
+	switch (ret) {
+	case 0:
+		return 0;
+		/* error described by POSIX:                                    */
+		/* EINTR  The nanosleep() function was interrupted by a signal. */
+		/* The C11 wording is:                                          */
+		/* -1 if it has been interrupted by a signal                    */
+	case -EINTR:
+		return -1;
+		/* EINVAL: described by POSIX */
+		/* EFAULT: described for linux */
+	default:
+		return -2;
+	}
+}
diff --git a/src/time/timespec_get.c b/src/time/timespec_get.c
new file mode 100644
index 0000000..20080a0
--- /dev/null
+++ b/src/time/timespec_get.c
@@ -0,0 +1,31 @@
+#include <time.h>
+#include "syscall.h"
+#include "atomic.h"
+
+static int syscall_clock_gettime(clockid_t clk, struct timespec *ts)
+{
+	return __syscall(SYS_clock_gettime, clk, ts);
+}
+
+void *__vdsosym(const char *, const char *);
+
+/* There is no other implemented value than TIME_UTC, all other values
+   are considered erroneous. */
+int timespec_get(struct timespec * ts, int base)
+{
+	if (base != TIME_UTC) return 0;
+	int ret;
+#ifdef VDSO_CGT_SYM
+	static int (*cgt)(clockid_t, struct timespec *);
+	if (!cgt) {
+		void *f = __vdsosym(VDSO_CGT_VER, VDSO_CGT_SYM);
+		if (!f) f = (void *)syscall_clock_gettime;
+		a_cas_p(&cgt, 0, f);
+	}
+	/* The vdso variants never fail, and thus never set errno. */
+	ret = cgt(CLOCK_REALTIME, ts);
+#else
+	ret = syscall_clock_gettime(CLOCK_REALTIME, ts);
+#endif
+	return ret < 0 ? 0 : base;
+}
-- 
1.7.10.4