[COMMIT osv master] libc: add minimal implementation of clock_nanosleep()

[Commit Bot]

From: Waldemar Kozaczuk <jwkoz...@gmail.com>
Committer: Nadav Har'El <n...@scylladb.com>
Branch: master

libc: add minimal implementation of clock_nanosleep()

This patch adds minimal implementation of clock_nanosleep() and
corresponding syscall that is enough to support glibc implementation
of the userland function nanosleep() which delegates to:

__syscall(clock_nanosleep, CLOCK_REALTIME, 0, req, rem)

In other words, the new clock_nanosleep() only implements
scenario where clock_id is CLOCK_REALTIME and flags is 0.

Please note that there is a patch sent to the mailing list
that implements the non-zero (TIMER_ABSTIME) scenario which is useful
in realtime scheduler scenarios.

Signed-off-by: Waldemar Kozaczuk <jwkoz...@gmail.com>

Closes #1244

---
diff --git a/exported_symbols/osv_ld-musl.so.1.symbols b/exported_symbols/osv_ld-musl.so.1.symbols
--- a/exported_symbols/osv_ld-musl.so.1.symbols
+++ b/exported_symbols/osv_ld-musl.so.1.symbols
@@ -76,6 +76,7 @@ clock
clock_getcpuclockid
clock_getres
clock_gettime
+clock_nanosleep
close
closedir
closelog
diff --git a/exported_symbols/osv_libc.so.6.symbols b/exported_symbols/osv_libc.so.6.symbols
--- a/exported_symbols/osv_libc.so.6.symbols
+++ b/exported_symbols/osv_libc.so.6.symbols
@@ -53,6 +53,7 @@ clock
clock_getcpuclockid
clock_getres
clock_gettime
+clock_nanosleep
close
closedir
closelog
diff --git a/libc/time.cc b/libc/time.cc
--- a/libc/time.cc
+++ b/libc/time.cc
@@ -40,6 +40,23 @@ int nanosleep(const struct timespec* req, struct timespec* rem)
return 0;
}

+OSV_LIBC_API
+int clock_nanosleep(clockid_t clock_id, int flags,
+ const struct timespec *request,
+ struct timespec *remain)
+{
+ //We ignore the "remain" argument same way we do it above in nanosleep()
+ //This argument is only relevant if the "sleeping" thread is interrupted
+ //by signals. But OSv signal implementation is limited and would not allow
+ //for such a scenario and both nanosleep() and clock_nanosleep() would
+ //never return EINTR
+ if (flags || clock_id != CLOCK_REALTIME) {
+ return ENOTSUP;
+ }
+ sched::thread::sleep(std::chrono::nanoseconds(convert(*request)));
+ return 0;
+}
+
OSV_LIBC_API
int usleep(useconds_t usec)
{
diff --git a/linux.cc b/linux.cc
--- a/linux.cc
+++ b/linux.cc
@@ -533,6 +533,7 @@ OSV_LIBC_API long syscall(long number, ...)
SYSCALL3(sys_getdents64, int, void *, size_t);
SYSCALL4(renameat, int, const char *, int, const char *);
SYSCALL1(sys_brk, void *);
+ SYSCALL4(clock_nanosleep, clockid_t, int, const struct timespec *, struct timespec *);
}

debug_always("syscall(): unimplemented system call %d\n", number);