Implement nanosleep per https://pubs.opengroup.org/onlinepubs/009695399/basedefs/time.h.html

[rtenneti]

Summary

Tested:
Limited unit test: This makes a call and checks that no error was
returned, but we currently don't have the ability to ensure that
time has elapsed as expected.

Co-authored-by: Jeff Bailey <[e-mail]>

[rtenneti]

Hi Siva,

Jeff and I worked on this. Please take a look. Thanks

[sivachandra]

libc/include/llvm-libc-types/CMakeLists.txt

38 ↗

(On Diff #460949)

Since this depends on time_t.h, we should add a DEPENDS .time_t.

libc/include/llvm-libc-types/struct_timespec.h

17

I think this definition is correct as per the POSIX spec. But, since we are passing structures of this shape to the Linux syscall, we should probably add a comment or TODO in src/time/nanosleep.cpp explaining why this definition is sufficient or incomplete.

libc/spec/stdc.td

17 ↗

(On Diff #460949)

Can you do the changes in the file separately as an obvious change?

libc/src/time/mktime.h

1 ↗

(On Diff #460949)

Can you make the changes in this file also separately?

libc/test/src/time/nanosleep_test.cpp

22

Call it SmokeTest may be? Also, move the above comment inside this test block.

[rtenneti]

Fixed comments.

[rtenneti]

Fixed comments.

libc/config/linux/aarch64/entrypoints.txt

list(APPEND TARGET_LIBC_ENTRYPOINTS
     libc.src.threads.tss_set
 
     # time.h entrypoints
     libc.src.time.asctime
     libc.src.time.asctime_r
     libc.src.time.gmtime
     libc.src.time.gmtime_r
     libc.src.time.mktime
+    libc.src.time.nanosleep
   )
 endif()
 
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}
 )

libc/config/linux/api.td

let Types = [
     "size_t",
     "__bsearchcompare_t",
     "__qsortcompare_t",
     "__atexithandler_t",
   ];
 }
 
 def TimeAPI : PublicAPI<"time.h"> {
-  let Types = ["time_t", "struct tm"];
+  let Types = ["time_t", "struct tm", "struct timespec"];
 }
 
 def ErrnoAPI : PublicAPI<"errno.h"> {
   let Macros = [
     ErrnoMacro,
     // We largely depend on linux/errno.h to give us the
     // various error macro definitions. However, some libc
     // implementations have chosen to provide definitions

libc/config/linux/x86_64/entrypoints.txt

list(APPEND TARGET_LIBC_ENTRYPOINTS
     libc.src.threads.tss_set
 
     # time.h entrypoints
     libc.src.time.asctime
     libc.src.time.asctime_r
     libc.src.time.gmtime
     libc.src.time.gmtime_r
     libc.src.time.mktime
+    libc.src.time.nanosleep
   )
 endif()
 
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}
 )

libc/include/CMakeLists.txt

 add_gen_header(
   time
   DEF_FILE time.h.def
   GEN_HDR time.h
   DEPENDS
     .llvm_libc_common_h
     .llvm-libc-types.time_t
     .llvm-libc-types.struct_tm
+    .llvm-libc-types.struct_timespec
 )
 
 add_gen_header(
   threads
   DEF_FILE threads.h.def
   GEN_HDR threads.h
   DEPENDS
     .llvm_libc_common_h

libc/include/llvm-libc-types/struct_timespec.h

 //===-- Definition of struct timespec -------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef __LLVM_LIBC_TYPES_TIMESPEC_H__
 #define __LLVM_LIBC_TYPES_TIMESPEC_H__
 
 #include <llvm-libc-types/time_t.h>
 
 struct timespec {
-  time_t tv_sec;
-  long tv_nsec;
+  time_t tv_sec; /* Seconds.  */
+  /* TODO: BIG_ENDIAN may require padding. */
+  long tv_nsec; /* Nanoseconds.  */
 };
 
 #endif // __LLVM_LIBC_TYPES_TIMESPEC_H__

libc/spec/posix.td

 def DIR : NamedType<"DIR">;
 def DIRPtr : PtrType<DIR>;
 def DIRRestrictedPtr : RestrictedPtrType<DIR>;
 def StructDirent : NamedType<"struct dirent">;
 def StructDirentPtr : PtrType<StructDirent>;
 def StructDirentPtrPtr : PtrType<StructDirentPtr>;
 def ConstStructDirentPtrPtr : ConstType<StructDirentPtrPtr>;
 
+def StructTimeSpec : NamedType<"struct timespec">;
+def StructTimeSpecPtr : PtrType<StructTimeSpec>;
+
 def POSIX : StandardSpec<"POSIX"> {
   PtrType CharPtr = PtrType<CharType>;
   RestrictedPtrType RestrictedCharPtr = RestrictedPtrType<CharType>;
   RestrictedPtrType CharRestrictedDoublePtr = RestrictedPtrType<CharPtr>;
   ConstType ConstCharPtr = ConstType<CharPtr>;
   ConstType ConstRestrictedCharPtr = ConstType<RestrictedCharPtr>;
 
   NamedType ModeTType = NamedType<"mode_t">;
HeaderSpec Dirent = HeaderSpec<
           FunctionSpec<
               "readdir",
               RetValSpec<StructDirentPtr>,
               [ArgSpec<DIRPtr>]
           >,
       ]
   >;
 
+  HeaderSpec Time = HeaderSpec<
+      "time.h",
+      [], // Macros
+      [StructTimeSpec], // Types
+      [], // Enumerations
+      [
+          FunctionSpec<
+              "nanosleep",
+              RetValSpec<IntType>,
+              [
+                ArgSpec<StructTimeSpecPtr>,
+                ArgSpec<StructTimeSpecPtr>,
+              ]
+          >,
+      ]
+  >;
+
   let Headers = [
     CType,
     Dirent,
     Errno,
     FCntl,
     PThread,
     Signal,
     StdIO,
     StdLib,
     SysMMan,
     SysResource,
     SysStat,
     SysUtsName,
+    Time,
     UniStd,
     String
   ];
 }

libc/src/time/CMakeLists.txt

add_entrypoint_object(
   HDRS
     mktime.h
   DEPENDS
     .time_utils
     libc.include.errno
     libc.include.time
     libc.src.errno.errno
 )
+
+add_entrypoint_object(
+  nanosleep
+  SRCS
+    nanosleep.cpp
+  HDRS
+    nanosleep.h
+  DEPENDS
+    libc.include.errno
+    libc.include.time
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

libc/src/time/nanosleep.h

+//===-- Implementation header of nanosleep -------------------------*- C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_TIME_NANOSLEEP_H
+#define LLVM_LIBC_SRC_TIME_NANOSLEEP_H
+
+#include <time.h>
+
+namespace __llvm_libc {
+
+int nanosleep(const struct timespec *req, struct timespec *rem);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_TIME_NANOSLEEP_H
+
+#include "include/time.h"

libc/src/time/nanosleep.cpp

+//===-- Implementation of nanosleep function
+//---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/time/nanosleep.h"
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "src/__support/OSUtil/syscall.h" // For syscall functions.
+#include "src/__support/common.h"
+
+#include <errno.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, nanosleep,
+                   (const struct timespec *req, struct timespec *rem)) {
+  int ret = __llvm_libc::syscall(SYS_nanosleep, req, rem);
+  if (ret < 0) {
+    errno = -ret;
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace __llvm_libc

libc/test/src/time/CMakeLists.txt

add_libc_unittest(
   HDRS
     TmHelper.h
     TmMatcher.h
   CXX_STANDARD
     20
   DEPENDS
     libc.src.time.mktime
 )
+
+add_libc_unittest(
+  nanosleep
+  SUITE
+    libc_time_unittests
+  SRCS
+    nanosleep_test.cpp
+  HDRS
+    TmHelper.h
+    TmMatcher.h
+  CXX_STANDARD
+    20
+  DEPENDS
+    libc.include.errno
+    libc.include.time
+    libc.src.time.nanosleep
+)

libc/test/src/time/nanosleep_test.cpp

+//===-- Unittests for nanosleep
+//---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <errno.h>
+#include <time.h>
+
+#include "src/time/nanosleep.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+namespace cpp = __llvm_libc::cpp;
+
+TEST(LlvmLibcNanosleep, SmokeTest) {
+  // TODO: When we have the code to read clocks, test that time has passed.
+  using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+  errno = 0;
+
+  struct timespec tim = {1, 500};
+  struct timespec tim2 = {0, 0};
+  int ret = __llvm_libc::nanosleep(&tim, &tim2);
+  ASSERT_EQ(errno, 0);
+  ASSERT_EQ(ret, 0);
+}