[libc] Fix scheduler test incorrectly guessing user privileges

[overmighty]

Non-root users may be able to set real-time scheduling policies. Don't
expect failure to set real-time scheduling policies based on UID.
Instead, check that if it fails, it is either due to missing privileges,
or unsupported parameters if the scheduling policy is not mandated by
POSIX.

Fixes #95564.

[llvmbot]

@llvm/pr-subscribers-libc

Author: OverMighty (overmighty)

Changes

These tests fail on Arch Linux, where setting these scheduling policies
succeeds even when not running as root.

---

Full diff: https://github.com/llvm/llvm-project/pull/95562.diff

1 Files Affected:

• (modified) libc/test/src/sched/param_and_scheduler_test.cpp (+5-3)

diff --git a/libc/test/src/sched/param_and_scheduler_test.cpp b/libc/test/src/sched/param_and_scheduler_test.cpp
index 8e81f2ed1517f..7cf553f1af525 100644
--- a/libc/test/src/sched/param_and_scheduler_test.cpp
+++ b/libc/test/src/sched/param_and_scheduler_test.cpp
@@ -145,9 +145,11 @@ class SchedTest : public LIBC_NAMESPACE::testing::Test {
   using LlvmLibcSchedTest = SchedTest;                                         \
   TEST_F(LlvmLibcSchedTest, Sched_##policy) { testSched(policy, can_set); }
 
-// Root is required to set these policies.
-LIST_SCHED_TESTS(SCHED_FIFO, LIBC_NAMESPACE::getuid() == 0)
-LIST_SCHED_TESTS(SCHED_RR, LIBC_NAMESPACE::getuid() == 0)
+// Temporarily disabled as these tests are failing on Arch Linux where
+// scheduling policy setting succeeds without running as root.
+// // Root is required to set these policies.
+// LIST_SCHED_TESTS(SCHED_FIFO, LIBC_NAMESPACE::getuid() == 0)
+// LIST_SCHED_TESTS(SCHED_RR, LIBC_NAMESPACE::getuid() == 0)
 
 // No root is required to set these policies.
 LIST_SCHED_TESTS(SCHED_OTHER, true)

[overmighty]

I don't have write access to the repo, could someone merge this for me please?