Kernel+LibC+UE: Implement usleep() via sys$clock_nanosleep()

This doesn't need to be its own syscall. Thanks @BenWiederhake for
the idea. :^)

DevTools/UserspaceEmulator/Emulator.cpp

@@ -272,8 +272,6 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
         return virt$ioctl(arg1, arg2, arg3);
     case SC_get_dir_entries:
         return virt$get_dir_entries(arg1, arg2, arg3);
-    case SC_usleep:
-        return virt$usleep(arg1);
     case SC_shbuf_create:
         return virt$shbuf_create(arg1, arg2);
     case SC_shbuf_allow_pid:
@@ -384,11 +382,6 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
     }
 }
 
-int Emulator::virt$usleep(useconds_t us)
-{
-    return syscall(SC_usleep, us);
-}
-
 int Emulator::virt$shbuf_create(int size, FlatPtr buffer)
 {
     u8* host_data = nullptr;

DevTools/UserspaceEmulator/Emulator.h

@@ -85,7 +85,6 @@ private:
     int virt$stat(FlatPtr);
     int virt$realpath(FlatPtr);
     int virt$gethostname(FlatPtr, ssize_t);
-    int virt$usleep(useconds_t);
     int virt$shbuf_create(int size, FlatPtr buffer);
     int virt$shbuf_allow_pid(int, pid_t peer_pid);
     int virt$shbuf_allow_all(int);

Kernel/API/Syscall.h

@@ -117,7 +117,6 @@ namespace Kernel {
     S(poll)                   \
     S(rmdir)                  \
     S(chmod)                  \
-    S(usleep)                 \
     S(socket)                 \
     S(bind)                   \
     S(accept)                 \
@@ -241,7 +240,7 @@ struct ImmutableBufferArgument {
 };
 
 struct StringListArgument {
-    Userspace<StringArgument*> strings { };
+    Userspace<StringArgument*> strings {};
     size_t length { 0 };
 };
 

Kernel/Syscalls/sleep.cpp

@@ -29,17 +29,6 @@
 
 namespace Kernel {
 
-int Process::sys$usleep(useconds_t usec)
-{
-    REQUIRE_PROMISE(stdio);
-    if (!usec)
-        return 0;
-    u64 wakeup_time = Thread::current()->sleep(usec * TimeManagement::the().ticks_per_second() / 1000000);
-    if (wakeup_time > g_uptime)
-        return -EINTR;
-    return 0;
-}
-
 int Process::sys$sleep(unsigned seconds)
 {
     REQUIRE_PROMISE(stdio);

Libraries/LibC/unistd.cpp

@@ -42,6 +42,7 @@
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <termios.h>
+#include <time.h>
 #include <unistd.h>
 
 extern "C" {
@@ -336,7 +337,8 @@ int sleep(unsigned seconds)
 
 int usleep(useconds_t usec)
 {
-    return syscall(SC_usleep, usec);
+    struct timespec ts = { (long)(usec / 1000000), (long)(usec % 1000000) * 1000 };
+    return clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, nullptr);
 }
 
 int gethostname(char* buffer, size_t size)