[libc-commits] [libc] [libc] Implement getpriority, setpriority, their unit tests; add the accompanying macros and type headers. (PR #219573)

via libc-commits libc-commits at lists.llvm.org
Fri Aug 28 14:00:08 PDT 2026 

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Vadim Kotov (vadimkotov)

<details>
<summary>Changes</summary>

Testing these is a bit tricky, what I've currently settled on is this.

- For `getpriority`
  - We make sure the call succeeds and then round-trip the highest nice value on Linux (19).
- For `setpriority`
  - We make sure the call succeeds when setting it to the current nice.
- For both
  - Test two failure modes that are easy to stably induce.

Since these calls are effectively glorified syscall wrappers, even though the above tests don't cover every case in which these functions are used, I think this may be sufficient to show that we correctly propagate values to the kernel and get the correct nice back.

---

Patch is 20.06 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/219573.diff


19 Files Affected:

- (modified) libc/config/linux/aarch64/entrypoints.txt (+2) 
- (modified) libc/config/linux/riscv/entrypoints.txt (+2) 
- (modified) libc/config/linux/x86_64/entrypoints.txt (+2) 
- (modified) libc/hdr/types/CMakeLists.txt (+8) 
- (added) libc/hdr/types/id_t.h (+27) 
- (modified) libc/include/llvm-libc-macros/linux/sys-resource-macros.h (+4) 
- (modified) libc/include/sys/resource.yaml (+21) 
- (modified) libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt (+26) 
- (added) libc/src/__support/OSUtil/linux/syscall_wrappers/getpriority.h (+34) 
- (added) libc/src/__support/OSUtil/linux/syscall_wrappers/setpriority.h (+34) 
- (modified) libc/src/sys/resource/CMakeLists.txt (+14) 
- (added) libc/src/sys/resource/getpriority.h (+26) 
- (modified) libc/src/sys/resource/linux/CMakeLists.txt (+28) 
- (added) libc/src/sys/resource/linux/getpriority.cpp (+34) 
- (added) libc/src/sys/resource/linux/setpriority.cpp (+33) 
- (added) libc/src/sys/resource/setpriority.h (+26) 
- (modified) libc/test/src/sys/resource/CMakeLists.txt (+31) 
- (added) libc/test/src/sys/resource/getpriority_test.cpp (+48) 
- (added) libc/test/src/sys/resource/setpriority_test.cpp (+39) 


``````````diff
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index 567025e62f43d..05bc74fa6932f 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -299,8 +299,10 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.random.getrandom
 
     # sys/resource.h entrypoints
+    libc.src.sys.resource.getpriority
     libc.src.sys.resource.getrlimit
     libc.src.sys.resource.getrusage
+    libc.src.sys.resource.setpriority
     libc.src.sys.resource.setrlimit
 
     # sys/sendfile.h entrypoints
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index 40fef13470322..cf28d6d9645e8 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -330,8 +330,10 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.random.getrandom
 
     # sys/resource.h entrypoints
+    libc.src.sys.resource.getpriority
     libc.src.sys.resource.getrlimit
     libc.src.sys.resource.getrusage
+    libc.src.sys.resource.setpriority
     libc.src.sys.resource.setrlimit
 
     # sys/sendfile.h entrypoints
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 6a37d8b2b48d6..2e1dc645696ee 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -330,8 +330,10 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.random.getrandom
 
     # sys/resource.h entrypoints
+    libc.src.sys.resource.getpriority
     libc.src.sys.resource.getrlimit
     libc.src.sys.resource.getrusage
+    libc.src.sys.resource.setpriority
     libc.src.sys.resource.setrlimit
 
     # sys/sem.h entrypoints
diff --git a/libc/hdr/types/CMakeLists.txt b/libc/hdr/types/CMakeLists.txt
index 14f5004922606..0d12917200226 100644
--- a/libc/hdr/types/CMakeLists.txt
+++ b/libc/hdr/types/CMakeLists.txt
@@ -1349,3 +1349,11 @@ add_proxy_header_library(
   FULL_BUILD_DEPENDS
     libc.include.llvm-libc-types.tcflag_t
 )
+
+add_proxy_header_library(
+  id_t
+  HDRS
+    id_t.h
+  FULL_BUILD_DEPENDS
+    libc.include.llvm-libc-types.id_t
+)
diff --git a/libc/hdr/types/id_t.h b/libc/hdr/types/id_t.h
new file mode 100644
index 0000000000000..b478af776b7cb
--- /dev/null
+++ b/libc/hdr/types/id_t.h
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Proxy for id_t.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_HDR_TYPES_ID_T_H
+#define LLVM_LIBC_HDR_TYPES_ID_T_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-types/id_t.h"
+
+#else // Overlay mode
+
+#include <sys/types.h>
+
+#endif // LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_TYPES_ID_T_H
diff --git a/libc/include/llvm-libc-macros/linux/sys-resource-macros.h b/libc/include/llvm-libc-macros/linux/sys-resource-macros.h
index 9f1e04a339c73..4c3ebf3991086 100644
--- a/libc/include/llvm-libc-macros/linux/sys-resource-macros.h
+++ b/libc/include/llvm-libc-macros/linux/sys-resource-macros.h
@@ -34,4 +34,8 @@
 #define RUSAGE_CHILDREN (-1)
 #define RUSAGE_THREAD 1
 
+#define PRIO_PROCESS 0
+#define PRIO_PGRP 1
+#define PRIO_USER 2
+
 #endif // LLVM_LIBC_MACROS_LINUX_SYS_RESOURCE_MACROS_H
diff --git a/libc/include/sys/resource.yaml b/libc/include/sys/resource.yaml
index a26dfb5f77beb..c4733dead7575 100644
--- a/libc/include/sys/resource.yaml
+++ b/libc/include/sys/resource.yaml
@@ -12,6 +12,12 @@ macros:
     macro_header: sys-resource-macros.h
     standards:
       - gnu
+  - macro_name: PRIO_PROCESS
+    macro_header: sys-resource-macros.h
+  - macro_name: PRIO_PGRP
+    macro_header: sys-resource-macros.h
+  - macro_name: PRIO_USER
+    macro_header: sys-resource-macros.h
 types:
   - type_name: struct_rlimit
   - type_name: rlim_t
@@ -19,6 +25,13 @@ types:
 enums: []
 objects: []
 functions:
+  - name: getpriority
+    standards:
+      - posix
+    return_type: int
+    arguments:
+      - type: int
+      - type: id_t
   - name: getrlimit
     standards:
       - posix
@@ -33,6 +46,14 @@ functions:
     arguments:
       - type: int
       - type: struct rusage *
+  - name: setpriority
+    standards:
+      - posix
+    return_type: int
+    arguments:
+      - type: int
+      - type: id_t
+      - type: int
   - name: setrlimit
     standards:
       - posix
diff --git a/libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt b/libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt
index 7d09f46696308..24371d2220921 100644
--- a/libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt
+++ b/libc/src/__support/OSUtil/linux/syscall_wrappers/CMakeLists.txt
@@ -1066,3 +1066,29 @@ add_header_library(
     libc.src.__support.macros.config
     libc.include.sys_syscall
 )
+
+add_header_library(
+  getpriority
+  HDRS
+    getpriority.h
+  DEPENDS
+    libc.hdr.types.id_t
+    libc.src.__support.OSUtil.osutil
+    libc.src.__support.common
+    libc.src.__support.error_or
+    libc.src.__support.macros.config
+    libc.include.sys_syscall
+)
+
+add_header_library(
+  setpriority
+  HDRS
+    setpriority.h
+  DEPENDS
+    libc.hdr.types.id_t
+    libc.src.__support.OSUtil.osutil
+    libc.src.__support.common
+    libc.src.__support.error_or
+    libc.src.__support.macros.config
+    libc.include.sys_syscall
+)
diff --git a/libc/src/__support/OSUtil/linux/syscall_wrappers/getpriority.h b/libc/src/__support/OSUtil/linux/syscall_wrappers/getpriority.h
new file mode 100644
index 0000000000000..d4939568528cf
--- /dev/null
+++ b/libc/src/__support/OSUtil/linux/syscall_wrappers/getpriority.h
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Syscall wrapper for getpriority
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_GETPRIORITY_H
+#define LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_GETPRIORITY_H
+
+#include "hdr/types/pid_t.h"
+#include "src/__support/OSUtil/linux/syscall.h" // For syscall_checked
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+#include <sys/syscall.h> // For syscall numbers
+
+namespace LIBC_NAMESPACE_DECL {
+namespace linux_syscalls {
+
+LIBC_INLINE ErrorOr<int> getpriority(int which, id_t who) {
+  return syscall_checked<int>(SYS_getpriority, which, who);
+}
+
+} // namespace linux_syscalls
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_GETPRIORITY_H
diff --git a/libc/src/__support/OSUtil/linux/syscall_wrappers/setpriority.h b/libc/src/__support/OSUtil/linux/syscall_wrappers/setpriority.h
new file mode 100644
index 0000000000000..0d3b7ede81f8a
--- /dev/null
+++ b/libc/src/__support/OSUtil/linux/syscall_wrappers/setpriority.h
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Syscall wrapper for setpriority
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_SETPRIORITY_H
+#define LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_SETPRIORITY_H
+
+#include "hdr/types/id_t.h"
+#include "src/__support/OSUtil/linux/syscall.h" // For syscall_checked
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+#include <sys/syscall.h> // For syscall numbers
+
+namespace LIBC_NAMESPACE_DECL {
+namespace linux_syscalls {
+
+LIBC_INLINE ErrorOr<int> setpriority(int which, id_t who, int niceval) {
+  return syscall_checked<int>(SYS_setpriority, which, who, niceval);
+}
+
+} // namespace linux_syscalls
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_OSUTIL_LINUX_SYSCALL_WRAPPERS_SETPRIORITY_H
diff --git a/libc/src/sys/resource/CMakeLists.txt b/libc/src/sys/resource/CMakeLists.txt
index ac5f676588994..7105eb98e67ac 100644
--- a/libc/src/sys/resource/CMakeLists.txt
+++ b/libc/src/sys/resource/CMakeLists.txt
@@ -2,6 +2,13 @@ if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
 endif()
 
+add_entrypoint_object(
+  getpriority
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.getpriority
+)
+
 add_entrypoint_object(
   getrlimit
   ALIAS
@@ -16,6 +23,13 @@ add_entrypoint_object(
     .${LIBC_TARGET_OS}.getrusage
 )
 
+add_entrypoint_object(
+  setpriority
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.setpriority
+)
+
 add_entrypoint_object(
   setrlimit
   ALIAS
diff --git a/libc/src/sys/resource/getpriority.h b/libc/src/sys/resource/getpriority.h
new file mode 100644
index 0000000000000..ca89889f0a190
--- /dev/null
+++ b/libc/src/sys/resource/getpriority.h
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation header of getpriority
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_RESOURCE_GETPRIORITY_H
+#define LLVM_LIBC_SRC_SYS_RESOURCE_GETPRIORITY_H
+
+#include "hdr/types/id_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int getpriority(int which, id_t who);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_RESOURCE_GETPRIORITY_H
diff --git a/libc/src/sys/resource/linux/CMakeLists.txt b/libc/src/sys/resource/linux/CMakeLists.txt
index 2a7d96c2eb365..293acb3337355 100644
--- a/libc/src/sys/resource/linux/CMakeLists.txt
+++ b/libc/src/sys/resource/linux/CMakeLists.txt
@@ -1,3 +1,17 @@
+add_entrypoint_object(
+  getpriority
+  SRCS
+    getpriority.cpp
+  HDRS
+    ../getpriority.h
+  DEPENDS
+    libc.hdr.types.id_t
+    libc.src.__support.OSUtil.linux.syscall_wrappers.getpriority
+    libc.src.__support.common
+    libc.src.__support.macros.config
+    libc.src.errno.errno
+)
+
 add_entrypoint_object(
   getrlimit
   SRCS
@@ -24,6 +38,20 @@ add_entrypoint_object(
     libc.src.errno.errno
 )
 
+add_entrypoint_object(
+  setpriority
+  SRCS
+    setpriority.cpp
+  HDRS
+    ../setpriority.h
+  DEPENDS
+    libc.hdr.types.id_t
+    libc.src.__support.OSUtil.linux.syscall_wrappers.setpriority
+    libc.src.__support.common
+    libc.src.__support.macros.config
+    libc.src.errno.errno
+)
+
 add_entrypoint_object(
   setrlimit
   SRCS
diff --git a/libc/src/sys/resource/linux/getpriority.cpp b/libc/src/sys/resource/linux/getpriority.cpp
new file mode 100644
index 0000000000000..a8c1225120c48
--- /dev/null
+++ b/libc/src/sys/resource/linux/getpriority.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Linux implementation of getpriority.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/resource/getpriority.h"
+
+#include "hdr/types/id_t.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/getpriority.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, getpriority, (int which, id_t who)) {
+  auto result = linux_syscalls::getpriority(which, who);
+  if (!result) {
+    libc_errno = result.error();
+    return -1;
+  }
+  // The syscall returns (20 - nice), but we must return nice itself.
+  return 20 - result.value();
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/resource/linux/setpriority.cpp b/libc/src/sys/resource/linux/setpriority.cpp
new file mode 100644
index 0000000000000..c22802ad0184e
--- /dev/null
+++ b/libc/src/sys/resource/linux/setpriority.cpp
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Linux implementation of setpriority.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/resource/setpriority.h"
+
+#include "hdr/types/id_t.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/setpriority.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, setpriority, (int which, id_t who, int prio)) {
+  auto result = linux_syscalls::setpriority(which, who, prio);
+  if (!result) {
+    libc_errno = result.error();
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/sys/resource/setpriority.h b/libc/src/sys/resource/setpriority.h
new file mode 100644
index 0000000000000..bcfd2a422882a
--- /dev/null
+++ b/libc/src/sys/resource/setpriority.h
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation header of setpriority
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_RESOURCE_SETPRIORITY_H
+#define LLVM_LIBC_SRC_SYS_RESOURCE_SETPRIORITY_H
+
+#include "hdr/types/id_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int setpriority(int which, id_t who, int prio);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_RESOURCE_SETPRIORITY_H
diff --git a/libc/test/src/sys/resource/CMakeLists.txt b/libc/test/src/sys/resource/CMakeLists.txt
index 5ff3ec8a62ea9..7e926a9e2996e 100644
--- a/libc/test/src/sys/resource/CMakeLists.txt
+++ b/libc/test/src/sys/resource/CMakeLists.txt
@@ -1,5 +1,20 @@
 add_custom_target(libc_sys_resource_unittests)
 
+add_libc_test(
+  getpriority_test
+  SUITE
+    libc_sys_resource_unittests
+  SRCS
+    getpriority_test.cpp
+  DEPENDS
+    libc.hdr.sys_resource_macros
+    libc.hdr.types.id_t
+    libc.src.sys.resource.getpriority
+    libc.src.sys.resource.setpriority
+    libc.test.UnitTest.ErrnoCheckingTest
+    libc.test.UnitTest.ErrnoSetterMatcher
+)
+
 add_libc_test(
   getrlimit_setrlimit_test
   SUITE
@@ -34,3 +49,19 @@ add_libc_test(
     libc.test.UnitTest.ErrnoCheckingTest
     libc.test.UnitTest.ErrnoSetterMatcher
 )
+
+add_libc_test(
+  setpriority_test
+  SUITE
+    libc_sys_resource_unittests
+  SRCS
+    setpriority_test.cpp
+  DEPENDS
+    libc.hdr.sys_resource_macros
+    libc.hdr.types.id_t
+    libc.src.sys.resource.getpriority
+    libc.src.sys.resource.setpriority
+    libc.test.UnitTest.ErrnoCheckingTest
+    libc.test.UnitTest.ErrnoSetterMatcher
+)
+
diff --git a/libc/test/src/sys/resource/getpriority_test.cpp b/libc/test/src/sys/resource/getpriority_test.cpp
new file mode 100644
index 0000000000000..567a344c1bb03
--- /dev/null
+++ b/libc/test/src/sys/resource/getpriority_test.cpp
@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Unittests for getpriority.
+///
+//===----------------------------------------------------------------------===//
+
+#include "hdr/sys_resource_macros.h"
+#include "hdr/types/id_t.h"
+#include "src/sys/resource/getpriority.h"
+#include "src/sys/resource/setpriority.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
+using LlvmLibcGetpriorityTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+TEST_F(LlvmLibcGetpriorityTest, BasicTest) {
+  int current_nice = LIBC_NAMESPACE::getpriority(PRIO_PROCESS, 0);
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_GE(current_nice, -20);
+  ASSERT_LE(current_nice, 19);
+
+  // Increase to the max on Linux (i.e. minimal priority, which doesn't require
+  // special privileges), so that we can confirm we get it back correctly.
+  int nice = 19;
+  // Make sure we're not setting it to the same priority by chance. If the below
+  // assertion ever fails, we'll need to re-think this test.
+  ASSERT_GT(nice, current_nice);
+
+  ASSERT_THAT(LIBC_NAMESPACE::setpriority(PRIO_PROCESS, 0, nice), Succeeds());
+  ASSERT_THAT(LIBC_NAMESPACE::getpriority(PRIO_PROCESS, 0), Succeeds(nice));
+}
+
+TEST_F(LlvmLibcGetpriorityTest, TestBadPid) {
+  ASSERT_THAT(LIBC_NAMESPACE::getpriority(PRIO_PROCESS, -1), Fails(ESRCH, -1));
+}
+
+TEST_F(LlvmLibcGetpriorityTest, TestBadWho) {
+  ASSERT_THAT(LIBC_NAMESPACE::getpriority(99, 0), Fails(EINVAL, -1));
+}
diff --git a/libc/test/src/sys/resource/setpriority_test.cpp b/libc/test/src/sys/resource/setpriority_test.cpp
new file mode 100644
index 0000000000000..0483eac9665ee
--- /dev/null
+++ b/libc/test/src/sys/resource/setpriority_test.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Unittests for setpriority.
+///
+//===----------------------------------------------------------------------===//
+
+#include "hdr/sys_resource_macros.h"
+#include "hdr/types/id_t.h"
+#include "src/sys/resource/getpriority.h"
+#include "src/sys/resource/setpriority.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
+using LlvmLibcSetpriorityTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+TEST_F(LlvmLibcSetpriorityTest, BasicTest) {
+  int nice = LIBC_NAMESPACE::getpriority(PRIO_PROCESS, 0);
+  ASSERT_ERRNO_SUCCESS();
+
+  ASSERT_THAT(LIBC_NAMESPACE::setpriority(PRIO_PROCESS, 0, nice), Succeeds());
+}
+
+TEST_F(LlvmLibcSetpriorityTest, TestBadPid) {
+  ASSERT_THAT(LIBC_NAMESPACE::setpriority(PRIO_PROCESS, -1, 19),
+              Fails(ESRCH, -1));
+}
+
+TEST_F(LlvmLibcSetpriorityTest, TestBadWho) {
+  ASSERT_THAT(L...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/219573

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