[libc-commits] [PATCH] D147985: [LIBC] Implement `sched_yield()`

[Noah Goldstein via Phabricator via libc-commits]

goldstein.w.n created this revision.
Herald added subscribers: libc-commits, ecnelises, tschuett.
Herald added projects: libc-project, All.
goldstein.w.n requested review of this revision.

Implements: https://linux.die.net/man/2/sched_yield

Possibly we don't need the return value check / errno as according to
both the manpage (and current linux source) `sched_yield` cannot fail.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D147985

Files:
  libc/src/sched/linux/CMakeLists.txt
  libc/src/sched/linux/sched_yield.cpp
  libc/src/sched/sched_yield.h


Index: libc/src/sched/sched_yield.h
===================================================================
--- /dev/null
+++ libc/src/sched/sched_yield.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for sched_yield -------------------*- 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_SCHED_SCHED_YIELD_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_YIELD_H
+
+namespace __llvm_libc {
+
+int sched_yield(void);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_YIELD_H
Index: libc/src/sched/linux/sched_yield.cpp
===================================================================
--- /dev/null
+++ libc/src/sched/linux/sched_yield.cpp
@@ -0,0 +1,28 @@
+//===-- Implementation of sched_yield -------------------------------------===//
+//
+// 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/sched/sched_yield.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, sched_yield, ()) {
+  long ret = __llvm_libc::syscall_impl(SYS_sched_yield);
+  // As of writing this, yield() cannot fail
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc
Index: libc/src/sched/linux/CMakeLists.txt
===================================================================
--- libc/src/sched/linux/CMakeLists.txt
+++ libc/src/sched/linux/CMakeLists.txt
@@ -30,4 +30,16 @@
     ../sched_getcpucount.h
   DEPENDS
     libc.include.sched
+  )
+
+add_entrypoint_object(
+  sched_yield
+  SRCS
+    sched_yield.cpp
+  HDRS
+    ../sched_yield.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
 )


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