[libc-commits] [libc] [libc] Implement sched_getcpu (PR #195001)
via libc-commits
libc-commits at lists.llvm.org
Wed Apr 29 21:40:53 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libc
Author: Aiden Grossman (boomanaiden154)
<details>
<summary>Changes</summary>
This is extremely similar to getcpu, but was available in a much earlier glibc, so a lot more code depends on it. Do a similar implementation. We can only have a simple smoke test as the only documented failure mode in the man page is running on a kernel that does not support the system call, and such kernels (<2.6) are ancient at this point.
---
Full diff: https://github.com/llvm/llvm-project/pull/195001.diff
8 Files Affected:
- (modified) libc/config/linux/x86_64/entrypoints.txt (+1)
- (modified) libc/include/sched.yaml (+6)
- (modified) libc/src/sched/CMakeLists.txt (+7)
- (modified) libc/src/sched/linux/CMakeLists.txt (+11)
- (added) libc/src/sched/linux/sched_getcpu.cpp (+31)
- (added) libc/src/sched/sched_getcpu.h (+20)
- (modified) libc/test/src/sched/CMakeLists.txt (+12)
- (added) libc/test/src/sched/sched_getcpu_test.cpp (+19)
``````````diff
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index d1c1d9496af67..54f2280a8d9a3 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -41,6 +41,7 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.sched.sched_get_priority_max
libc.src.sched.sched_get_priority_min
libc.src.sched.sched_getaffinity
+ libc.src.sched.sched_getcpu
libc.src.sched.sched_getparam
libc.src.sched.sched_getscheduler
libc.src.sched.sched_rr_get_interval
diff --git a/libc/include/sched.yaml b/libc/include/sched.yaml
index b75dee3000449..d08b875aaa6ce 100644
--- a/libc/include/sched.yaml
+++ b/libc/include/sched.yaml
@@ -52,6 +52,12 @@ functions:
- type: pid_t
- type: size_t
- type: cpu_set_t *
+ - name: sched_getcpu
+ standards:
+ - GNUExtensions
+ return_type: int
+ arguments:
+ - type: void
- name: sched_getparam
standards:
- POSIX
diff --git a/libc/src/sched/CMakeLists.txt b/libc/src/sched/CMakeLists.txt
index d1d1de0718c56..39ac8c8c6f247 100644
--- a/libc/src/sched/CMakeLists.txt
+++ b/libc/src/sched/CMakeLists.txt
@@ -16,6 +16,13 @@ add_entrypoint_object(
.${LIBC_TARGET_OS}.sched_getaffinity
)
+add_entrypoint_object(
+ sched_getcpu
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.sched_getcpu
+)
+
add_entrypoint_object(
sched_setaffinity
ALIAS
diff --git a/libc/src/sched/linux/CMakeLists.txt b/libc/src/sched/linux/CMakeLists.txt
index ceb755f8e1d1a..6cc41e97baa00 100644
--- a/libc/src/sched/linux/CMakeLists.txt
+++ b/libc/src/sched/linux/CMakeLists.txt
@@ -24,6 +24,17 @@ add_entrypoint_object(
libc.src.errno.errno
)
+add_entrypoint_object(
+ sched_getcpu
+ SRCS
+ sched_getcpu.cpp
+ HDRS
+ ../sched_getcpu.h
+ DEPENDS
+ libc.src.__support.OSUtil.osutil
+ libc.src.errno.errno
+)
+
add_entrypoint_object(
sched_setaffinity
SRCS
diff --git a/libc/src/sched/linux/sched_getcpu.cpp b/libc/src/sched/linux/sched_getcpu.cpp
new file mode 100644
index 0000000000000..2c58440e3c73f
--- /dev/null
+++ b/libc/src/sched/linux/sched_getcpu.cpp
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_getcpu.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, sched_getcpu, ()) {
+ int cpu = 0;
+ int ret =
+ LIBC_NAMESPACE::syscall_impl<int>(SYS_getcpu, cpu, nullptr, nullptr);
+ if (ret < 0) {
+ libc_errno = -ret;
+ return -1;
+ }
+ return cpu;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sched/sched_getcpu.h b/libc/src/sched/sched_getcpu.h
new file mode 100644
index 0000000000000..6e6857cc33b4f
--- /dev/null
+++ b/libc/src/sched/sched_getcpu.h
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_GETCPU_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_GETCPU_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int sched_getcpu(void);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_GETCPU_H
diff --git a/libc/test/src/sched/CMakeLists.txt b/libc/test/src/sched/CMakeLists.txt
index 93752ed26108d..5c6c90f40194f 100644
--- a/libc/test/src/sched/CMakeLists.txt
+++ b/libc/test/src/sched/CMakeLists.txt
@@ -56,6 +56,18 @@ add_libc_unittest(
libc.test.UnitTest.ErrnoCheckingTest
)
+add_libc_unittest(
+ sched_getcpu_test
+ SUITE
+ libc_sched_unittests
+ SRCS
+ sched_getcpu_test.cpp
+ DEPENDS
+ libc.src.errno.errno
+ libc.src.sched.sched_getcpu
+ libc.test.UnitTest.ErrnoCheckingTest
+)
+
add_libc_unittest(
scheduler_test
SUITE
diff --git a/libc/test/src/sched/sched_getcpu_test.cpp b/libc/test/src/sched/sched_getcpu_test.cpp
new file mode 100644
index 0000000000000..7953294c3459e
--- /dev/null
+++ b/libc/test/src/sched/sched_getcpu_test.cpp
@@ -0,0 +1,19 @@
+//===-- Unittests for getcpu ----------------------------------------------===//
+//
+// 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/__support/OSUtil/syscall.h"
+#include "src/sched/sched_getcpu.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+
+using LlvmLibcSchedSchedGetCpuTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+TEST_F(LlvmLibcSchedSchedGetCpuTest, SmokeTest) {
+ using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+ ASSERT_THAT(LIBC_NAMESPACE::sched_getcpu(), Succeeds());
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/195001
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