chrt: (man) explain which kernel config options are needed for SCHED_EXT

On systems running kernel version 6.12+ it is still possible
that the syscall to set SCHED_EXT fails with EINVAL, this can
happen when certain kernel configuration options have not been
set. The list of required options can be found here:
https://docs.kernel.org/scheduler/sched-ext.html#switching-to-and-from-sched-ext

Let's document this in the man page to give users a heads up.

Signed-off-by: Christian Goeschel Ndjomouo <cgoesc2@wgu.edu>

diff --git a/schedutils/chrt.1.adoc b/schedutils/chrt.1.adoc
index ec08fd721e94569e671e8b5f2cf7bcec8670d7a0..b8d8874bca821f47c3d1618370a4cabc26338628 100644 (file)
--- a/schedutils/chrt.1.adoc
+++ b/schedutils/chrt.1.adoc
@@ -68,6 +68,7 @@ Set scheduling policy to *SCHED_DEADLINE* (sporadic task model deadline scheduli
 
 *-e*, *--ext*::
 Set scheduling policy to *SCHED_EXT* (BPF program-defined scheduling). Linux-specific, supported since 6.12. Since util-linux v2.42, the priority argument is optional; if specified, it must be set to zero.
+Note that for the policy to be recognized, the following kernel configuration options need to be enabled: *CONFIG_BPF*, *CONFIG_SCHED_CLASS_EXT*, *CONFIG_BPF_SYSCALL*, *CONFIG_BPF_JIT*, *CONFIG_DEBUG_INFO_BTF*, *CONFIG_BPF_JIT_ALWAYS_ON* and *CONFIG_BPF_JIT_DEFAULT_ON*.
 
 == SCHEDULING OPTIONS