[LIBC] Implement remainder of posix 'sched.h' minus `SCHED_SPORADIC`

[goldstein.w.n]

Summary

Includes macros:

linux/SCHED_OTHER // posix req
linux/SCHED_FIFO // posix req
linux/SCHED_RR // posix req
linux/SCHED_BATCH
linux/SCHED_ISO
linux/SCHED_IDLE
linux/SCHED_DEADLINE

Includes types:

struct sched_param { int sched_priority; }

Includes functions:

sched_setparam
sched_getparam
sched_setscheduler
sched_getscheduler
sched_get_priority_max
sched_get_priority_min
sched_rr_get_interval

[goldstein.w.n]

Fix misdef

[michaelrj]

some initial comments, will do a more thorough review later today.

libc/spec/posix.td

49

this shouldn't be StructTimeSpecPtr

libc/src/sched/linux/sched_get_priority_max.cpp

21

does this syscall not have a name?

[goldstein.w.n]

libc/src/sched/linux/sched_get_priority_max.cpp

21

Bah, will fix from debugging (was forgetting to return ret but went a bit crazy first).

[michaelrj]

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

22–36

if we don't expect to need SCHED_SPORADIC then we can leave this part out of the struct for the moment.

libc/test/src/sched/get_priority_test.cpp

36

given that there are relatively few of these it's probably better to just repeat the code of the test. It makes the file longer, but it also makes debugging easier. The ASSERT macros only report the line they're on and the failing value, so if one of these is failing it'll be hard to tell from the error which it is. If you want to you can use the {braces} to scope each of the tests, that way redefining the variables each time won't be an issue.

50

if you want, you could split the failures into a separate test.

libc/test/src/sched/param_and_scheduler_test.cpp

28–29

nit: formatting?

139–141

each of these should probably be in their own test.

libc/test/src/sched/rr_get_interval_test.cpp

37 ↗

(On Diff #512922)

where is getuid included from?

[goldstein.w.n]

libc/test/src/sched/rr_get_interval_test.cpp

37 ↗

(On Diff #512922)

Hmm, so it seems the test is not actually building/running. I double checked the cmakelist and it seems right. Any idea whats going on?

[goldstein.w.n]

Fix issues

[sivachandra]

libc/include/llvm-libc-macros/linux/sched-macros.h

15

Can you add a comment explaining how these numbers were picked? If they were picked to be in sync with the Linux kernel, mention the kernel header which defines them.

libc/include/llvm-libc-macros/sched-macros.h

14 ↗

(On Diff #513032)

Same here.

libc/test/src/sched/rr_get_interval_test.cpp

1 ↗

(On Diff #513032)

Extra n.

1 ↗

(On Diff #513032)

Also, why is the file not named sched_rr_get_interval_test.cpp.

[goldstein.w.n]

libc/test/src/sched/rr_get_interval_test.cpp

1 ↗

(On Diff #513032)

Renamed, was just following the norm of the direction which seems to be to omit sched_ prefix.

[goldstein.w.n]

Fix nits

[sivachandra]

Few more nits but I will let @michaelrj drive this review.

libc/include/llvm-libc-macros/linux/sched-macros.h

13

Instead of Copy ..., say something like, The definitions here match those in linux/sched.h.

libc/include/llvm-libc-macros/sched-macros.h

13 ↗

(On Diff #513312)

Ditto.

16 ↗

(On Diff #513312)

I missed this last time: These definitions are also based on linux/sched.h so they should stay in linux/sched-macros.h?

[goldstein.w.n]

libc/include/llvm-libc-macros/sched-macros.h

16 ↗

(On Diff #513312)

I missed this last time: These definitions are also based on linux/sched.h so they should stay in linux/sched-macros.h?

Yeah that's probably best. The reason I put them in generic is they are required for POSIX, not Linux extensions.

[goldstein.w.n]

Cleanup sched.h macros

[michaelrj]

I think with these last few changes it should be good to go. I want to test it before it lands so I'll approve once that's done.

libc/test/src/sched/get_priority_test.cpp

17

Even if sched isn't in the filename, it should be in the test title since this is what shows up when you run the test. Same for the other tests.

libc/test/src/sched/sched_rr_get_interval_test.cpp

39

for clarity, this should be ::getuid since it's coming from the system's libc.

[goldstein.w.n]

clarify test / getuid()

[goldstein.w.n]

Update td after moving macros

[sivachandra]

libc/include/llvm-libc-macros/sched-macros.h

13 ↗

(On Diff #513312)

Remove these commented out lines - it will become a precedent for new patches otherwise.

libc/test/src/sched/sched_rr_get_interval_test.cpp

39

LLVM's libc has getuid so why don't we just use __llvm_libc::getuid here?

[goldstein.w.n]

Remove comments, use llvm-libc getuid

[michaelrj]

LGTM, tests pass on my end. I've left a few nits but feel free to land once they're fixed

libc/spec/posix.td

640

this should still have CpuSetT in the Types list since it's used by sched_getcpucount

646

not relevant for this patch, but in a future patch it would be good to add the argument ArgSpect<VoidType> here. In C a function with no arguments is interpreted as having unspecified parameters, whereas a function with an argument of void has no arguments.

libc/test/src/sched/param_and_scheduler_test.cpp

38

nit: These test enough functionality that they probably shouldn't be called smoke tests. I'd recommend just calling this SchedOtherTest and same for the rest below.

[goldstein.w.n]

SmokeTest -> Test

libc/spec/posix.td

640

sched_getcpucount is gnu extension though. We have CpuSetT in gnu.td.

646

+1, is there an issue we add it now (not supported), or just leave it as todo?

As an side, what are these files for? I've had bugs in them but libc compiled fine /tests ran.

[michaelrj]

libc/spec/posix.td

640

ah, you're right. Nevermind then.

646

You can fix it now or leave a TODO and fix it in a followup patch, either works.

These files are used to generate the header files in fullbuild mode. We have a TableGen based utility called HeaderGen that takes in the api.td file for the platform you're building for. Then the api.td file includes these files in the spec folder. These files tell HeaderGen what the function prototypes for each function are, and which header file they go in. Then the entrypoints.txt and headers.txt files determine which functions and headers should be built for this specific platform. If you want to see the header files then build libc-headers and look in build/projects/libc/include, though make sure you've set LLVM_LIBC_FULL_BUILD to ON in your cmake. If you want to test that these work, then run the libc-api-test which uses the PrototypeTestGen (in libc/utils/HdrGen/PrototypeTestGen/PrototypeTestGen.cpp) to generate the prototypes for each function, then test that they match the implementation.

[goldstein.w.n]

Make yield void

[goldstein.w.n]

libc/spec/posix.td

646

not relevant for this patch, but in a future patch it would be good to add the argument ArgSpect<VoidType> here. In C a function with no arguments is interpreted as having unspecified parameters, whereas a function with an argument of void has no arguments.

Done for yield. Will do in the future.

646

You can fix it now or leave a TODO and fix it in a followup patch, either works.

These files are used to generate the header files in fullbuild mode. We have a TableGen based utility called HeaderGen that takes in the api.td file for the platform you're building for. Then the api.td file includes these files in the spec folder. These files tell HeaderGen what the function prototypes for each function are, and which header file they go in. Then the entrypoints.txt and headers.txt files determine which functions and headers should be built for this specific platform. If you want to see the header files then build libc-headers and look in build/projects/libc/include, though make sure you've set LLVM_LIBC_FULL_BUILD to ON in your cmake. If you want to test that these work, then run the libc-api-test which uses the PrototypeTestGen (in libc/utils/HdrGen/PrototypeTestGen/PrototypeTestGen.cpp) to generate the prototypes for each function, then test that they match the implementation.

Ahh makes sense. Thanks :)

libc/config/linux/aarch64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.errno.errno
 
     # fcntl.h entrypoints
     libc.src.fcntl.creat
     libc.src.fcntl.open
     libc.src.fcntl.openat
 
     # sched.h entrypoints
+    libc.src.sched.sched_get_priority_max
+    libc.src.sched.sched_get_priority_min
     libc.src.sched.sched_getaffinity
+    libc.src.sched.sched_getparam
+    libc.src.sched.sched_getscheduler
+    libc.src.sched.sched_rr_get_interval
     libc.src.sched.sched_setaffinity
+    libc.src.sched.sched_setparam
+    libc.src.sched.sched_setscheduler
     libc.src.sched.sched_yield
 
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.index
     libc.src.string.memccpy

libc/config/linux/api.td

let Types = [
     "struct tm",
     "struct timespec",
     "struct timeval",
     "clockid_t",
   ];
 }
 
 def SchedAPI : PublicAPI<"sched.h"> {
-  let Types = ["pid_t", "size_t", "cpu_set_t"];
+  let Types = [
+    "pid_t",
+    "size_t",
+    "cpu_set_t",
+    "struct sched_param",
+    // Needed according to posix standard
+    "time_t",
+    "struct timespec",
+  ];
 }
 
 def SysMManAPI : PublicAPI<"sys/mman.h"> {
   let Types = ["off_t", "size_t"];
 }
 
 def SignalAPI : PublicAPI<"signal.h"> {
   let Types = [

libc/config/linux/riscv64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.errno.errno
 
     # fcntl.h entrypoints
     libc.src.fcntl.creat
     libc.src.fcntl.open
     libc.src.fcntl.openat
 
     # sched.h entrypoints
+    libc.src.sched.sched_get_priority_max
+    libc.src.sched.sched_get_priority_min
     libc.src.sched.sched_getaffinity
+    libc.src.sched.sched_getparam
+    libc.src.sched.sched_getscheduler
+    libc.src.sched.sched_rr_get_interval
     libc.src.sched.sched_setaffinity
+    libc.src.sched.sched_setparam
+    libc.src.sched.sched_setscheduler
     libc.src.sched.sched_yield
 
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.index
     libc.src.string.memccpy

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.errno.errno
 
     # fcntl.h entrypoints
     libc.src.fcntl.creat
     libc.src.fcntl.open
     libc.src.fcntl.openat
 
     # sched.h entrypoints
+    libc.src.sched.sched_get_priority_max
+    libc.src.sched.sched_get_priority_min
     libc.src.sched.sched_getaffinity
+    libc.src.sched.sched_getparam
+    libc.src.sched.sched_getscheduler
+    libc.src.sched.sched_rr_get_interval
     libc.src.sched.sched_setaffinity
+    libc.src.sched.sched_setparam
+    libc.src.sched.sched_setscheduler
     libc.src.sched.sched_yield
 
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.index
     libc.src.string.memccpy

libc/include/CMakeLists.txt

 
 add_gen_header(
   sched
   DEF_FILE sched.h.def
   GEN_HDR sched.h
   DEPENDS
     .llvm_libc_common_h
     .llvm-libc-macros.sched_macros
+    .llvm-libc-types.cpu_set_t
     .llvm-libc-types.pid_t
     .llvm-libc-types.size_t
-    .llvm-libc-types.cpu_set_t
+    .llvm-libc-types.struct_sched_param
+    # Needed according to posix standard
+    .llvm-libc-types.time_t
+    .llvm-libc-types.struct_timespec
 )
 
 add_gen_header(
   spawn
   DEF_FILE spawn.h.def
   GEN_HDR spawn.h
   DEPENDS
     .llvm_libc_common_h

libc/include/llvm-libc-macros/linux/sched-macros.h

 //===-- Definition of macros from sched.h ---------------------------------===//
 //
 // 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_MACROS_LINUX_SCHED_MACROS_H
 #define __LLVM_LIBC_MACROS_LINUX_SCHED_MACROS_H
 
+// Definitions of SCHED_* macros must match was linux as at:
+// https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/sched.h
+
+// Posix required
+#define SCHED_OTHER 0
+#define SCHED_FIFO 1
+#define SCHED_RR 2
+
+// Linux extentions
+#define SCHED_BATCH 3
+#define SCHED_ISO 4 // Not yet implemented, reserved.
+#define SCHED_IDLE 5
+#define SCHED_DEADLINE 6
+
 #define CPU_COUNT_S(setsize, set) __sched_getcpucount(setsize, set)
 #define CPU_COUNT(set) CPU_COUNT_S(sizeof(cpu_set_t), set)
 
 #endif // __LLVM_LIBC_MACROS_LINUX_SCHED_MACROS_H

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

 add_header(rlim_t HDR rlim_t.h)
 add_header(time_t HDR time_t.h)
 add_header(stack_t HDR stack_t.h)
 add_header(suseconds_t HDR suseconds_t.h)
 add_header(struct_timeval HDR struct_timeval.h DEPENDS .suseconds_t .time_t)
 add_header(struct_rlimit HDR struct_rlimit.h DEPENDS .rlim_t)
 add_header(struct_rusage HDR struct_rusage.h DEPENDS .struct_timeval)
 add_header(struct_dirent HDR struct_dirent.h DEPENDS .ino_t .off_t)
+add_header(struct_sched_param HDR struct_sched_param.h)
 add_header(union_sigval HDR union_sigval.h)
 add_header(siginfo_t HDR siginfo_t.h DEPENDS .union_sigval .pid_t .uid_t)
 add_header(sig_atomic_t HDR sig_atomic_t.h)
 add_header(sigset_t HDR sigset_t.h DEPENDS libc.include.llvm-libc-macros.signal_macros)
 add_header(struct_sigaction HDR struct_sigaction.h DEPENDS .sigset_t .siginfo_t)
 add_header(struct_timespec HDR struct_timespec.h DEPENDS .time_t)
 add_header(
   struct_stat

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

+//===-- Definition of type struct sched_param -----------------------------===//
+//
+// 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_STRUCT_SCHED_PARAM_H__
+#define __LLVM_LIBC_TYPES_STRUCT_SCHED_PARAM_H__
+
+#include <llvm-libc-types/pid_t.h>
+#include <llvm-libc-types/struct_timespec.h>
+#include <llvm-libc-types/time_t.h>
+
+struct sched_param {
+  // Process or thread execution scheduling priority.
+  int sched_priority;
+};
+
+#endif // __LLVM_LIBC_TYPES_STRUCT_SCHED_PARAM_H__

libc/spec/linux.td

HeaderSpec Errno = HeaderSpec<
         Macro<"ENOTNAM">,
         Macro<"ELNRNG">,
         Macro<"EL2NSYNC">,
         Macro<"EADV">,
         Macro<"ECOMM">,
       ]
   >;
 
+  HeaderSpec Sched = HeaderSpec<
+      "sched.h",
+      [
+        Macro<"SCHED_OTHER">,
+        Macro<"SCHED_FIFO">,
+        Macro<"SCHED_RR">,
+        Macro<"SCHED_BATCH">,
+        Macro<"SCHED_ISO">,
+        Macro<"SCHED_IDLE">,
+        Macro<"SCHED_DEADLINE">,
+      ],
+      [], // Types
+      [], // Enumerations
+      []  // Functions
+  >;
+
   HeaderSpec SysMMan = HeaderSpec<
       "sys/mman.h",
       [Macro<"MAP_ANONYMOUS">]
   >;
 
 
   HeaderSpec SysPrctl = HeaderSpec<
       "sys/prctl.h",

libc/spec/posix.td

 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 StructSchedParam : NamedType<"struct sched_param">;
+def StructSchedParamPtr : PtrType<StructSchedParam>;
+def ConstStructSchedParamPtr : ConstType<StructSchedParamPtr>;
+
 def ExecArgvT : NamedType<"__exec_argv_t">;
 def ExecEnvpT : NamedType<"__exec_envp_t">;
 
 def AtForkCallbackT : NamedType<"__atfork_callback_t">;
 
 def PosixSpawnFileActionsT : NamedType<"posix_spawn_file_actions_t">;
 def PosixSpawnFileActionsTPtr : PtrType<PosixSpawnFileActionsT>;
 def ConstPosixSpawnFileActionsTPtr : ConstType<PosixSpawnFileActionsTPtr>;
[
           [ArgSpec<ConstCharPtr>]
         >,
     ]
   >;
 
   HeaderSpec Sched = HeaderSpec<
       "sched.h",
       [], // Macros
-      [PidT, SizeTType, CpuSetT], // Types
+      [PidT, TimeTType, StructTimeSpec, StructSchedParam], // Types
       [], // Enumerations
       [
         FunctionSpec<
             "sched_yield",
             RetValSpec<IntType>,
             []
         >,
+        FunctionSpec<
+            "sched_setparam",
+            RetValSpec<IntType>,
+            [ArgSpec<PidT>, ArgSpec<ConstStructSchedParamPtr>]
+        >,
+
+        FunctionSpec<
+            "sched_getparam",
+            RetValSpec<IntType>,
+            [ArgSpec<PidT>, ArgSpec<StructSchedParamPtr>]
+        >,
+
+        FunctionSpec<
+            "sched_setscheduler",
+            RetValSpec<IntType>,
+            [ArgSpec<PidT>]
+        >,
+
+        FunctionSpec<
+            "sched_getscheduler",
+            RetValSpec<IntType>,
+            [ArgSpec<PidT>, ArgSpec<IntType>, ArgSpec<ConstStructSchedParamPtr>]
+        >,
+
+        FunctionSpec<
+            "sched_get_priority_min",
+            RetValSpec<IntType>,
+            [ArgSpec<IntType>]
+        >,
+
+        FunctionSpec<
+            "sched_get_priority_max",
+            RetValSpec<IntType>,
+            [ArgSpec<IntType>]
+        >,
+
+        FunctionSpec<
+            "sched_rr_get_interval",
+            RetValSpec<IntType>,
+            [ArgSpec<PidT>, ArgSpec<StructTimeSpecPtr>]
+        >,
       ]
   >;
 
   HeaderSpec String = HeaderSpec<
     "string.h",
     [
         Macro<"NULL">,
     ],

libc/src/sched/CMakeLists.txt

 add_entrypoint_object(
   sched_yield
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.sched_yield
 )
 
 add_entrypoint_object(
+  sched_setparam
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sched_setparam
+)
+
+add_entrypoint_object(
+  sched_getparam
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sched_getparam
+)
+
+add_entrypoint_object(
+  sched_setscheduler
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sched_setscheduler
+)
+
+add_entrypoint_object(
+  sched_getscheduler
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sched_getscheduler
+)
+
+add_entrypoint_object(
+  sched_get_priority_min
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sched_get_priority_min
+)
+
+add_entrypoint_object(
+  sched_get_priority_max
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sched_get_priority_max
+)
+
+add_entrypoint_object(
+  sched_rr_get_interval
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sched_rr_get_interval
+)
+
+add_entrypoint_object(
   __sched_getcpucount
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.__sched_getcpucount
 )

libc/src/sched/linux/CMakeLists.txt

SRCS
     sched_yield.cpp
   HDRS
     ../sched_yield.h
   DEPENDS
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
 )
+
+add_entrypoint_object(
+  sched_setparam
+  SRCS
+    sched_setparam.cpp
+  HDRS
+    ../sched_setparam.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  sched_getparam
+  SRCS
+    sched_getparam.cpp
+  HDRS
+    ../sched_getparam.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  sched_setscheduler
+  SRCS
+    sched_setscheduler.cpp
+  HDRS
+    ../sched_setscheduler.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  sched_getscheduler
+  SRCS
+    sched_getscheduler.cpp
+  HDRS
+    ../sched_getscheduler.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  sched_get_priority_min
+  SRCS
+    sched_get_priority_min.cpp
+  HDRS
+    ../sched_get_priority_min.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  sched_get_priority_max
+  SRCS
+    sched_get_priority_max.cpp
+  HDRS
+    ../sched_get_priority_max.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  sched_rr_get_interval
+  SRCS
+    sched_rr_get_interval.cpp
+  HDRS
+    ../sched_rr_get_interval.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

libc/src/sched/linux/sched_get_priority_max.cpp

+//===-- Implementation of sched_get_priority_max --------------------------===//
+//
+// 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_get_priority_max.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, sched_get_priority_max, (int policy)) {
+  long ret = __llvm_libc::syscall_impl(SYS_sched_get_priority_min, policy);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace __llvm_libc

libc/src/sched/linux/sched_get_priority_min.cpp

+//===-- Implementation of sched_get_priority_min --------------------------===//
+//
+// 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_get_priority_min.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, sched_get_priority_min, (int policy)) {
+  long ret = __llvm_libc::syscall_impl(SYS_sched_get_priority_min, policy);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace __llvm_libc

libc/src/sched/linux/sched_getparam.cpp

+//===-- Implementation of sched_getparam ----------------------------------===//
+//
+// 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_getparam.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, sched_getparam,
+                   (pid_t tid, struct sched_param *param)) {
+  long ret = __llvm_libc::syscall_impl(SYS_sched_getparam, tid, param);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/sched/linux/sched_getscheduler.cpp

+//===-- Implementation of sched_getscheduler ------------------------------===//
+//
+// 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_getscheduler.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, sched_getscheduler, (pid_t tid)) {
+  long ret = __llvm_libc::syscall_impl(SYS_sched_getscheduler, tid);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/sched/linux/sched_rr_get_interval.cpp

+//===-- Implementation of sched_rr_get_interval ---------------------------===//
+//
+// 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_rr_get_interval.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, sched_rr_get_interval,
+                   (pid_t tid, struct timespec *tp)) {
+  long ret = __llvm_libc::syscall_impl(SYS_sched_rr_get_interval, tid, tp);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/sched/linux/sched_setparam.cpp

+//===-- Implementation of sched_setparam ----------------------------------===//
+//
+// 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_setparam.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, sched_setparam,
+                   (pid_t tid, const struct sched_param *param)) {
+  long ret = __llvm_libc::syscall_impl(SYS_sched_setparam, tid, param);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/sched/linux/sched_setscheduler.cpp

+//===-- Implementation of sched_setscheduler ------------------------------===//
+//
+// 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_setscheduler.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, sched_setscheduler,
+                   (pid_t tid, int policy, const struct sched_param *param)) {
+  long ret =
+      __llvm_libc::syscall_impl(SYS_sched_setscheduler, tid, policy, param);
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/sched/sched_get_priority_max.h

+//===-- Implementation header for sched_get_priority_max ---------*- 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_GET_PRIORITY_MAX_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_GET_PRIORITY_MAX_H
+
+namespace __llvm_libc {
+
+int sched_get_priority_max(int policy);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_GET_PRIORITY_MAX_H

libc/src/sched/sched_get_priority_min.h

+//===-- Implementation header for sched_get_priority_min ---------*- 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_GET_PRIORITY_MIN_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_GET_PRIORITY_MIN_H
+
+namespace __llvm_libc {
+
+int sched_get_priority_min(int policy);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_GET_PRIORITY_MIN_H

libc/src/sched/sched_getparam.h

+//===-- Implementation header for sched_getparam ----------------*- 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_GETPARAM_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_GETPARAM_H
+
+#include <sched.h>
+
+namespace __llvm_libc {
+
+int sched_getparam(pid_t tid, struct sched_param *param);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_GETPARAM_H

libc/src/sched/sched_getscheduler.h

+//===-- Implementation header for sched_getscheduler -------------*- 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_GETSCHEDULER_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_GETSCHEDULER_H
+
+#include <sched.h>
+
+namespace __llvm_libc {
+
+int sched_getscheduler(pid_t tid);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_GETSCHEDULER_H

libc/src/sched/sched_rr_get_interval.h

+//===-- Implementation header for sched_rr_get_interval ----------*- 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_RR_GET_INTERVAL_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_RR_GET_INTERVAL_H
+
+#include <sched.h>
+
+namespace __llvm_libc {
+
+int sched_rr_get_interval(pid_t tid, struct timespec *tp);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_RR_GET_INTERVAL_H

libc/src/sched/sched_setparam.h

+//===-- Implementation header for sched_setparam ----------------*- 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_SETPARAM_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_SETPARAM_H
+
+#include <sched.h>
+
+namespace __llvm_libc {
+
+int sched_setparam(pid_t tid, const struct sched_param *param);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_SETPARAM_H

libc/src/sched/sched_setscheduler.h

+//===-- Implementation header for sched_setscheduler -------------*- 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_SETSCHEDULER_H
+#define LLVM_LIBC_SRC_SCHED_SCHED_SETSCHEDULER_H
+
+#include <sched.h>
+
+namespace __llvm_libc {
+
+int sched_setscheduler(pid_t tid, int policy, const struct sched_param *param);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SCHED_SCHED_SETSCHEDULER_H

libc/test/src/sched/CMakeLists.txt

add_libc_unittest(
   SRCS
     yield_test.cpp
   DEPENDS
     libc.src.errno.errno
     libc.src.sched.sched_yield
 )
 
 add_libc_unittest(
+  get_priority_test
+  SUITE
+    libc_sched_unittests
+  SRCS
+    get_priority_test.cpp
+  DEPENDS
+    libc.include.sched
+    libc.src.errno.errno
+    libc.src.sched.sched_get_priority_min
+    libc.src.sched.sched_get_priority_max
+)
+
+add_libc_unittest(
+  scheduler_test
+  SUITE
+    libc_sched_unittests
+  SRCS
+    param_and_scheduler_test.cpp
+  DEPENDS
+    libc.include.sched
+    libc.src.errno.errno
+    libc.src.sched.sched_getscheduler
+    libc.src.sched.sched_setscheduler
+    libc.src.sched.sched_getparam
+    libc.src.sched.sched_setparam
+    libc.src.sched.sched_get_priority_min
+    libc.src.sched.sched_get_priority_max
+    libc.src.unistd.getuid
+)
+
+add_libc_unittest(
+  sched_rr_get_interval_test
+  SUITE
+    libc_sched_unittests
+  SRCS
+    sched_rr_get_interval_test.cpp
+  DEPENDS
+    libc.include.sched
+    libc.src.errno.errno
+    libc.src.sched.sched_getscheduler
+    libc.src.sched.sched_setscheduler
+    libc.src.sched.sched_get_priority_min
+    libc.src.sched.sched_rr_get_interval
+    libc.src.unistd.getuid
+)
+
+add_libc_unittest(
   cpu_count_test
   SUITE
     libc_sched_unittests
   SRCS
     cpu_count_test.cpp
   DEPENDS
     libc.include.sched
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
     libc.src.sched.sched_getaffinity
     libc.src.sched.__sched_getcpucount
     libc.test.errno_setter_matcher
 )

libc/test/src/sched/get_priority_test.cpp

+//===-- Unittests for sched_get_priority_{min,max} ------------------------===//
+//
+// 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/errno/libc_errno.h"
+#include "src/sched/sched_get_priority_max.h"
+#include "src/sched/sched_get_priority_min.h"
+#include "test/UnitTest/Test.h"
+
+#include <sched.h>
+
+TEST(LlvmLibcSchedGetPriorityTest, HandleBadPolicyTest) {
+
+  // Test arbitrary values for which there is no policy.
+  {
+    int policy = -1;
+    int max_priority = __llvm_libc::sched_get_priority_max(policy);
+    ASSERT_EQ(max_priority, -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    int min_priority = __llvm_libc::sched_get_priority_min(policy);
+    ASSERT_EQ(min_priority, -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+  }
+
+  {
+    int policy = 30;
+    int max_priority = __llvm_libc::sched_get_priority_max(policy);
+    ASSERT_EQ(max_priority, -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    int min_priority = __llvm_libc::sched_get_priority_min(policy);
+    ASSERT_EQ(min_priority, -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+  }
+
+  {
+    int policy = 80;
+    int max_priority = __llvm_libc::sched_get_priority_max(policy);
+    ASSERT_EQ(max_priority, -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    int min_priority = __llvm_libc::sched_get_priority_min(policy);
+    ASSERT_EQ(min_priority, -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+  }
+
+  {
+    int policy = 110;
+    int max_priority = __llvm_libc::sched_get_priority_max(policy);
+    ASSERT_EQ(max_priority, -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    int min_priority = __llvm_libc::sched_get_priority_min(policy);
+    ASSERT_EQ(min_priority, -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+  }
+}
+
+TEST(LlvmLibcSchedGetPriorityTest, SmokeTest) {
+  libc_errno = 0;
+
+  // We Test:
+  // SCHED_OTHER, SCHED_FIFO, SCHED_RR
+  // Linux specific test could also include:
+  // SCHED_BATCH, SCHED_ISO, SCHED_IDLE, SCHED_DEADLINE
+  {
+    int policy = SCHED_OTHER;
+    int max_priority = __llvm_libc::sched_get_priority_max(policy);
+    ASSERT_GE(max_priority, 0);
+    ASSERT_EQ(libc_errno, 0);
+    int min_priority = __llvm_libc::sched_get_priority_min(policy);
+    ASSERT_GE(min_priority, 0);
+    ASSERT_EQ(libc_errno, 0);
+
+    ASSERT_LE(max_priority, 99);
+    ASSERT_GE(min_priority, 0);
+    ASSERT_GE(max_priority, min_priority);
+  }
+
+  {
+    int policy = SCHED_FIFO;
+    int max_priority = __llvm_libc::sched_get_priority_max(policy);
+    ASSERT_GE(max_priority, 0);
+    ASSERT_EQ(libc_errno, 0);
+    int min_priority = __llvm_libc::sched_get_priority_min(policy);
+    ASSERT_GE(min_priority, 0);
+    ASSERT_EQ(libc_errno, 0);
+
+    ASSERT_LE(max_priority, 99);
+    ASSERT_GE(min_priority, 0);
+    ASSERT_GE(max_priority, min_priority);
+  }
+
+  {
+    int policy = SCHED_RR;
+    int max_priority = __llvm_libc::sched_get_priority_max(policy);
+    ASSERT_GE(max_priority, 0);
+    ASSERT_EQ(libc_errno, 0);
+    int min_priority = __llvm_libc::sched_get_priority_min(policy);
+    ASSERT_GE(min_priority, 0);
+    ASSERT_EQ(libc_errno, 0);
+
+    ASSERT_LE(max_priority, 99);
+    ASSERT_GE(min_priority, 0);
+    ASSERT_GE(max_priority, min_priority);
+  }
+}

libc/test/src/sched/param_and_scheduler_test.cpp

+//===-- Unittests for sched_{set,get}{scheduler,param} --------------------===//
+//
+// 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/errno/libc_errno.h"
+#include "src/sched/sched_get_priority_max.h"
+#include "src/sched/sched_get_priority_min.h"
+#include "src/sched/sched_getparam.h"
+#include "src/sched/sched_getscheduler.h"
+#include "src/sched/sched_setparam.h"
+#include "src/sched/sched_setscheduler.h"
+#include "src/unistd/getuid.h"
+#include "test/UnitTest/Test.h"
+
+#include <sched.h>
+
+// We Test:
+// SCHED_OTHER, SCHED_FIFO, SCHED_RR
+//
+// TODO: Missing two tests.
+//       1) Missing permissions -> EPERM. Maybe doable by finding
+//          another pid that exists and changing its policy, but that
+//          seems risky. Maybe something with fork/clone would work.
+//
+//       2) Unkown pid -> ESRCH. Probably safe to choose a large range
+//          number or scanning current pids and getting one that doesn't
+//          exist, but again seems like it may risk actually changing
+//          sched policy on a running task.
+//
+//       Linux specific test could also include:
+//          SCHED_BATCH, SCHED_ISO, SCHED_IDLE, SCHED_DEADLINE
+
+TEST(LlvmLibcSchedParamAndSchedulerTest, SchedOtherTest) {
+  libc_errno = 0;
+
+  int policy = SCHED_OTHER;
+  bool can_set = true;
+
+  int init_policy = __llvm_libc::sched_getscheduler(0);
+  ASSERT_GE(init_policy, 0);
+  ASSERT_EQ(libc_errno, 0);
+
+  int max_priority = __llvm_libc::sched_get_priority_max(policy);
+  ASSERT_GE(max_priority, 0);
+  ASSERT_EQ(libc_errno, 0);
+  int min_priority = __llvm_libc::sched_get_priority_min(policy);
+  ASSERT_GE(min_priority, 0);
+  ASSERT_EQ(libc_errno, 0);
+
+  struct sched_param param = {min_priority};
+
+  // Negative pid
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(-1, policy, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  ASSERT_EQ(__llvm_libc::sched_getscheduler(-1), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  // Invalid Policy
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy | 128, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  // Out of bounds priority
+  param.sched_priority = min_priority - 1;
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  param.sched_priority = max_priority + 1;
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param), -1);
+  // A bit hard to test as depending if we are root or not we can run into
+  // different issues.
+  ASSERT_TRUE(libc_errno == EINVAL || libc_errno == EPERM);
+  libc_errno = 0;
+
+  // Some sched policies require permissions, so skip
+  param.sched_priority = min_priority;
+  // Success / missing permissions.
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param),
+            can_set ? 0 : -1);
+  ASSERT_TRUE(can_set ? (libc_errno == 0)
+                      : (libc_errno == EINVAL || libc_errno == EPERM));
+  libc_errno = 0;
+
+  ASSERT_EQ(__llvm_libc::sched_getscheduler(0), can_set ? policy : init_policy);
+  ASSERT_EQ(libc_errno, 0);
+
+  // Out of bounds priority
+  param.sched_priority = -1;
+  ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  param.sched_priority = max_priority + 1;
+  ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  for (int priority = min_priority; priority <= max_priority; ++priority) {
+    ASSERT_EQ(__llvm_libc::sched_getparam(0, &param), 0);
+    ASSERT_EQ(libc_errno, 0);
+    int init_priority = param.sched_priority;
+
+    param.sched_priority = priority;
+
+    // Negative pid
+    ASSERT_EQ(__llvm_libc::sched_setparam(-1, &param), -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    libc_errno = 0;
+
+    ASSERT_EQ(__llvm_libc::sched_getparam(-1, &param), -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    libc_errno = 0;
+
+    // Success / missing permissions
+    ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), can_set ? 0 : -1);
+    ASSERT_TRUE(can_set ? (libc_errno == 0)
+                        : (libc_errno == EINVAL || libc_errno == EPERM));
+    libc_errno = 0;
+
+    ASSERT_EQ(__llvm_libc::sched_getparam(0, &param), 0);
+    ASSERT_EQ(libc_errno, 0);
+
+    ASSERT_EQ(param.sched_priority, can_set ? priority : init_priority);
+  }
+  // Null test
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, nullptr), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+}
+
+TEST(LlvmLibcSchedParamAndSchedulerTest, SchedFIFOTest) {
+  libc_errno = 0;
+
+  int policy = SCHED_FIFO;
+  bool can_set = __llvm_libc::getuid() == 0;
+
+  int init_policy = __llvm_libc::sched_getscheduler(0);
+  ASSERT_GE(init_policy, 0);
+  ASSERT_EQ(libc_errno, 0);
+
+  int max_priority = __llvm_libc::sched_get_priority_max(policy);
+  ASSERT_GE(max_priority, 0);
+  ASSERT_EQ(libc_errno, 0);
+  int min_priority = __llvm_libc::sched_get_priority_min(policy);
+  ASSERT_GE(min_priority, 0);
+  ASSERT_EQ(libc_errno, 0);
+
+  struct sched_param param = {min_priority};
+
+  // Negative pid
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(-1, policy, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  ASSERT_EQ(__llvm_libc::sched_getscheduler(-1), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  // Invalid Policy
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy | 128, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  // Out of bounds priority
+  param.sched_priority = min_priority - 1;
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  param.sched_priority = max_priority + 1;
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param), -1);
+  // A bit hard to test as depending if we are root or not we can run into
+  // different issues.
+  ASSERT_TRUE(libc_errno == EINVAL || libc_errno == EPERM);
+  libc_errno = 0;
+
+  // Some sched policies require permissions, so skip
+  param.sched_priority = min_priority;
+  // Success / missing permissions.
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param),
+            can_set ? 0 : -1);
+  ASSERT_TRUE(can_set ? (libc_errno == 0)
+                      : (libc_errno == EINVAL || libc_errno == EPERM));
+  libc_errno = 0;
+
+  ASSERT_EQ(__llvm_libc::sched_getscheduler(0), can_set ? policy : init_policy);
+  ASSERT_EQ(libc_errno, 0);
+
+  // Out of bounds priority
+  param.sched_priority = -1;
+  ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  param.sched_priority = max_priority + 1;
+  ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  for (int priority = min_priority; priority <= max_priority; ++priority) {
+    ASSERT_EQ(__llvm_libc::sched_getparam(0, &param), 0);
+    ASSERT_EQ(libc_errno, 0);
+    int init_priority = param.sched_priority;
+
+    param.sched_priority = priority;
+
+    // Negative pid
+    ASSERT_EQ(__llvm_libc::sched_setparam(-1, &param), -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    libc_errno = 0;
+
+    ASSERT_EQ(__llvm_libc::sched_getparam(-1, &param), -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    libc_errno = 0;
+
+    // Success / missing permissions
+    ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), can_set ? 0 : -1);
+    ASSERT_TRUE(can_set ? (libc_errno == 0)
+                        : (libc_errno == EINVAL || libc_errno == EPERM));
+    libc_errno = 0;
+
+    ASSERT_EQ(__llvm_libc::sched_getparam(0, &param), 0);
+    ASSERT_EQ(libc_errno, 0);
+
+    ASSERT_EQ(param.sched_priority, can_set ? priority : init_priority);
+  }
+  // Null test
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, nullptr), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+}
+
+TEST(LlvmLibcSchedParamAndSchedulerTest, SchedRRTest) {
+  libc_errno = 0;
+
+  int policy = SCHED_RR;
+  bool can_set = __llvm_libc::getuid() == 0;
+
+  int init_policy = __llvm_libc::sched_getscheduler(0);
+  ASSERT_GE(init_policy, 0);
+  ASSERT_EQ(libc_errno, 0);
+
+  int max_priority = __llvm_libc::sched_get_priority_max(policy);
+  ASSERT_GE(max_priority, 0);
+  ASSERT_EQ(libc_errno, 0);
+  int min_priority = __llvm_libc::sched_get_priority_min(policy);
+  ASSERT_GE(min_priority, 0);
+  ASSERT_EQ(libc_errno, 0);
+
+  struct sched_param param = {min_priority};
+
+  // Negative pid
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(-1, policy, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  ASSERT_EQ(__llvm_libc::sched_getscheduler(-1), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  // Invalid Policy
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy | 128, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  // Out of bounds priority
+  param.sched_priority = min_priority - 1;
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  param.sched_priority = max_priority + 1;
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param), -1);
+  // A bit hard to test as depending if we are root or not we can run into
+  // different issues.
+  ASSERT_TRUE(libc_errno == EINVAL || libc_errno == EPERM);
+  libc_errno = 0;
+
+  // Some sched policies require permissions, so skip
+  param.sched_priority = min_priority;
+  // Success / missing permissions.
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param),
+            can_set ? 0 : -1);
+  ASSERT_TRUE(can_set ? (libc_errno == 0)
+                      : (libc_errno == EINVAL || libc_errno == EPERM));
+  libc_errno = 0;
+
+  ASSERT_EQ(__llvm_libc::sched_getscheduler(0), can_set ? policy : init_policy);
+  ASSERT_EQ(libc_errno, 0);
+
+  // Out of bounds priority
+  param.sched_priority = -1;
+  ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  param.sched_priority = max_priority + 1;
+  ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  for (int priority = min_priority; priority <= max_priority; ++priority) {
+    ASSERT_EQ(__llvm_libc::sched_getparam(0, &param), 0);
+    ASSERT_EQ(libc_errno, 0);
+    int init_priority = param.sched_priority;
+
+    param.sched_priority = priority;
+
+    // Negative pid
+    ASSERT_EQ(__llvm_libc::sched_setparam(-1, &param), -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    libc_errno = 0;
+
+    ASSERT_EQ(__llvm_libc::sched_getparam(-1, &param), -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    libc_errno = 0;
+
+    // Success / missing permissions
+    ASSERT_EQ(__llvm_libc::sched_setparam(0, &param), can_set ? 0 : -1);
+    ASSERT_TRUE(can_set ? (libc_errno == 0)
+                        : (libc_errno == EINVAL || libc_errno == EPERM));
+    libc_errno = 0;
+
+    ASSERT_EQ(__llvm_libc::sched_getparam(0, &param), 0);
+    ASSERT_EQ(libc_errno, 0);
+
+    ASSERT_EQ(param.sched_priority, can_set ? priority : init_priority);
+  }
+  // Null test
+  ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, nullptr), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+}
+
+TEST(LlvmLibcSchedParamAndSchedulerTest, NullParamTest) {
+  libc_errno = 0;
+
+  ASSERT_EQ(__llvm_libc::sched_setparam(0, nullptr), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+
+  ASSERT_EQ(__llvm_libc::sched_getparam(0, nullptr), -1);
+  ASSERT_EQ(libc_errno, EINVAL);
+  libc_errno = 0;
+}

libc/test/src/sched/sched_rr_get_interval_test.cpp

+//===-- Unittests for sched_rr_get_interval -------------------------------===//
+//
+// 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/errno/libc_errno.h"
+#include "src/sched/sched_get_priority_min.h"
+#include "src/sched/sched_getscheduler.h"
+#include "src/sched/sched_rr_get_interval.h"
+#include "src/sched/sched_setscheduler.h"
+#include "src/unistd/getuid.h"
+#include "test/UnitTest/Test.h"
+
+#include <sched.h>
+
+TEST(LlvmLibcSchedRRGetIntervalTest, SmokeTest) {
+  libc_errno = 0;
+  auto SetSched = [&](int policy) {
+    int min_priority = __llvm_libc::sched_get_priority_min(policy);
+    ASSERT_GE(min_priority, 0);
+    ASSERT_EQ(libc_errno, 0);
+    struct sched_param param;
+    param.sched_priority = min_priority;
+    ASSERT_EQ(__llvm_libc::sched_setscheduler(0, policy, &param), 0);
+    ASSERT_EQ(libc_errno, 0);
+  };
+
+  auto TimespecToNs = [](struct timespec t) {
+    return t.tv_sec * 1000UL * 1000UL * 1000UL + t.tv_nsec;
+  };
+
+  struct timespec ts;
+
+  // We can only set SCHED_RR with CAP_SYS_ADMIN
+  if (__llvm_libc::getuid() == 0)
+    SetSched(SCHED_RR);
+
+  int cur_policy = __llvm_libc::sched_getscheduler(0);
+  ASSERT_GE(cur_policy, 0);
+  ASSERT_EQ(libc_errno, 0);
+
+  // We can actually run meaningful tests.
+  if (cur_policy == SCHED_RR) {
+    // Success
+    ASSERT_EQ(__llvm_libc::sched_rr_get_interval(0, &ts), 0);
+    ASSERT_EQ(libc_errno, 0);
+
+    // Check that numbers make sense (liberal bound of 10ns - 30sec)
+    ASSERT_GT(TimespecToNs(ts), 10UL);
+    ASSERT_LT(TimespecToNs(ts), 30UL * 1000UL * 1000UL * 1000UL);
+
+    // Null timespec
+    ASSERT_EQ(__llvm_libc::sched_rr_get_interval(0, nullptr), -1);
+    ASSERT_EQ(libc_errno, EFAULT);
+    libc_errno = 0;
+
+    // Negative pid
+    ASSERT_EQ(__llvm_libc::sched_rr_get_interval(-1, &ts), -1);
+    ASSERT_EQ(libc_errno, EINVAL);
+    libc_errno = 0;
+  }
+
+  // Negative tests don't have SCHED_RR set
+  SetSched(SCHED_OTHER);
+  ASSERT_EQ(__llvm_libc::sched_rr_get_interval(0, &ts), 0);
+  ASSERT_EQ(libc_errno, 0);
+  libc_errno = 0;
+
+  // TODO: Missing unkown pid -> ESRCH. This is read only so safe to try a few
+  //       unlikely values.
+}