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Message-Id: <aaebc5b34089d367a4fa1a9e8f35712bcaf3c8e5.1409423162.git.Jens.Gustedt@inria.fr>
Date: Sat, 30 Aug 2014 20:46:35 +0200
From: Jens Gustedt <Jens.Gustedt@...ia.fr>
To: musl@...ts.openwall.com
Subject: [PATCH 2/8] additions to src/time
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
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