commit a73f863af4ce9730795eab7097fb2102e6854365
author Juri Lelli <juri.lelli@redhat.com> Tue Oct 13 07:31:14 2020 +0200
committer Ingo Molnar <mingo@kernel.org> Wed Oct 14 19:55:46 2020 +0200
tree 340de06f8885734a43c9f6335a62599b7761fe88
parent eba9f08293d76370049ec85581ab3d7f6d069e3e

sched/features: Fix !CONFIG_JUMP_LABEL case

Commit:

  765cc3a4b224e ("sched/core: Optimize sched_feat() for !CONFIG_SCHED_DEBUG builds")

made sched features static for !CONFIG_SCHED_DEBUG configurations, but
overlooked the CONFIG_SCHED_DEBUG=y and !CONFIG_JUMP_LABEL cases.

For the latter echoing changes to /sys/kernel/debug/sched_features has
the nasty effect of effectively changing what sched_features reports,
but without actually changing the scheduler behaviour (since different
translation units get different sysctl_sched_features).

Fix CONFIG_SCHED_DEBUG=y and !CONFIG_JUMP_LABEL configurations by properly
restructuring ifdefs.

Fixes: 765cc3a4b224e ("sched/core: Optimize sched_feat() for !CONFIG_SCHED_DEBUG builds")
Co-developed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Patrick Bellasi <patrick.bellasi@matbug.net>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20201013053114.160628-1-juri.lelli@redhat.com

kernel/sched/core.c

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 8160ab5..d2003a7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -44,7 +44,7 @@
 
 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 
-#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_JUMP_LABEL)
+#ifdef CONFIG_SCHED_DEBUG
 /*
  * Debugging: various feature bits
  *

kernel/sched/sched.h

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 648f023..df80bfc 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1629,7 +1629,7 @@
 
 #undef SCHED_FEAT
 
-#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_JUMP_LABEL)
+#ifdef CONFIG_SCHED_DEBUG
 
 /*
  * To support run-time toggling of sched features, all the translation units
@@ -1637,6 +1637,7 @@
  */
 extern const_debug unsigned int sysctl_sched_features;
 
+#ifdef CONFIG_JUMP_LABEL
 #define SCHED_FEAT(name, enabled)					\
 static __always_inline bool static_branch_##name(struct static_key *key) \
 {									\
@@ -1649,7 +1650,13 @@
 extern struct static_key sched_feat_keys[__SCHED_FEAT_NR];
 #define sched_feat(x) (static_branch_##x(&sched_feat_keys[__SCHED_FEAT_##x]))
 
-#else /* !(SCHED_DEBUG && CONFIG_JUMP_LABEL) */
+#else /* !CONFIG_JUMP_LABEL */
+
+#define sched_feat(x) (sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
+
+#endif /* CONFIG_JUMP_LABEL */
+
+#else /* !SCHED_DEBUG */
 
 /*
  * Each translation unit has its own copy of sysctl_sched_features to allow
@@ -1665,7 +1672,7 @@
 
 #define sched_feat(x) !!(sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
 
-#endif /* SCHED_DEBUG && CONFIG_JUMP_LABEL */
+#endif /* SCHED_DEBUG */
 
 extern struct static_key_false sched_numa_balancing;
 extern struct static_key_false sched_schedstats;