sched/preempt: Move PREEMPT_DYNAMIC logic later

The PREEMPT_DYNAMIC logic in kernel/sched/core.c patches static calls
for a bunch of preemption functions. While most are defined prior to
this, the definition of cond_resched() is later in the file, and so we
only have its declarations from include/linux/sched.h.

In subsequent patches we'd like to define some macros alongside the
definition of each of the preemption functions, which we can use within
sched_dynamic_update(). For this to be possible, the PREEMPT_DYNAMIC
logic needs to be placed after the various preemption functions.

As a preparatory step, this patch moves the PREEMPT_DYNAMIC logic after
the various preemption functions, with no other changes -- this is
purely a move.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220214165216.2231574-2-mark.rutland@arm.com

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1e08b02..a123ffa 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6555,142 +6555,6 @@ EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
 
 #endif /* CONFIG_PREEMPTION */
 
-#ifdef CONFIG_PREEMPT_DYNAMIC
-
-#include <linux/entry-common.h>
-
-/*
- * SC:cond_resched
- * SC:might_resched
- * SC:preempt_schedule
- * SC:preempt_schedule_notrace
- * SC:irqentry_exit_cond_resched
- *
- *
- * NONE:
- *   cond_resched               <- __cond_resched
- *   might_resched              <- RET0
- *   preempt_schedule           <- NOP
- *   preempt_schedule_notrace   <- NOP
- *   irqentry_exit_cond_resched <- NOP
- *
- * VOLUNTARY:
- *   cond_resched               <- __cond_resched
- *   might_resched              <- __cond_resched
- *   preempt_schedule           <- NOP
- *   preempt_schedule_notrace   <- NOP
- *   irqentry_exit_cond_resched <- NOP
- *
- * FULL:
- *   cond_resched               <- RET0
- *   might_resched              <- RET0
- *   preempt_schedule           <- preempt_schedule
- *   preempt_schedule_notrace   <- preempt_schedule_notrace
- *   irqentry_exit_cond_resched <- irqentry_exit_cond_resched
- */
-
-enum {
-       preempt_dynamic_undefined = -1,
-       preempt_dynamic_none,
-       preempt_dynamic_voluntary,
-       preempt_dynamic_full,
-};
-
-int preempt_dynamic_mode = preempt_dynamic_undefined;
-
-int sched_dynamic_mode(const char *str)
-{
-       if (!strcmp(str, "none"))
-               return preempt_dynamic_none;
-
-       if (!strcmp(str, "voluntary"))
-               return preempt_dynamic_voluntary;
-
-       if (!strcmp(str, "full"))
-               return preempt_dynamic_full;
-
-       return -EINVAL;
-}
-
-void sched_dynamic_update(int mode)
-{
-       /*
-        * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
-        * the ZERO state, which is invalid.
-        */
-       static_call_update(cond_resched, __cond_resched);
-       static_call_update(might_resched, __cond_resched);
-       static_call_update(preempt_schedule, __preempt_schedule_func);
-       static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
-       static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
-
-       switch (mode) {
-       case preempt_dynamic_none:
-               static_call_update(cond_resched, __cond_resched);
-               static_call_update(might_resched, (void *)&__static_call_return0);
-               static_call_update(preempt_schedule, NULL);
-               static_call_update(preempt_schedule_notrace, NULL);
-               static_call_update(irqentry_exit_cond_resched, NULL);
-               pr_info("Dynamic Preempt: none\n");
-               break;
-
-       case preempt_dynamic_voluntary:
-               static_call_update(cond_resched, __cond_resched);
-               static_call_update(might_resched, __cond_resched);
-               static_call_update(preempt_schedule, NULL);
-               static_call_update(preempt_schedule_notrace, NULL);
-               static_call_update(irqentry_exit_cond_resched, NULL);
-               pr_info("Dynamic Preempt: voluntary\n");
-               break;
-
-       case preempt_dynamic_full:
-               static_call_update(cond_resched, (void *)&__static_call_return0);
-               static_call_update(might_resched, (void *)&__static_call_return0);
-               static_call_update(preempt_schedule, __preempt_schedule_func);
-               static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
-               static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
-               pr_info("Dynamic Preempt: full\n");
-               break;
-       }
-
-       preempt_dynamic_mode = mode;
-}
-
-static int __init setup_preempt_mode(char *str)
-{
-       int mode = sched_dynamic_mode(str);
-       if (mode < 0) {
-               pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);
-               return 0;
-       }
-
-       sched_dynamic_update(mode);
-       return 1;
-}
-__setup("preempt=", setup_preempt_mode);
-
-static void __init preempt_dynamic_init(void)
-{
-       if (preempt_dynamic_mode == preempt_dynamic_undefined) {
-               if (IS_ENABLED(CONFIG_PREEMPT_NONE)) {
-                       sched_dynamic_update(preempt_dynamic_none);
-               } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) {
-                       sched_dynamic_update(preempt_dynamic_voluntary);
-               } else {
-                       /* Default static call setting, nothing to do */
-                       WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT));
-                       preempt_dynamic_mode = preempt_dynamic_full;
-                       pr_info("Dynamic Preempt: full\n");
-               }
-       }
-}
-
-#else /* !CONFIG_PREEMPT_DYNAMIC */
-
-static inline void preempt_dynamic_init(void) { }
-
-#endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */
-
 /*
  * This is the entry point to schedule() from kernel preemption
  * off of irq context.
@@ -8271,6 +8135,142 @@ int __cond_resched_rwlock_write(rwlock_t *lock)
 }
 EXPORT_SYMBOL(__cond_resched_rwlock_write);
 
+#ifdef CONFIG_PREEMPT_DYNAMIC
+
+#include <linux/entry-common.h>
+
+/*
+ * SC:cond_resched
+ * SC:might_resched
+ * SC:preempt_schedule
+ * SC:preempt_schedule_notrace
+ * SC:irqentry_exit_cond_resched
+ *
+ *
+ * NONE:
+ *   cond_resched               <- __cond_resched
+ *   might_resched              <- RET0
+ *   preempt_schedule           <- NOP
+ *   preempt_schedule_notrace   <- NOP
+ *   irqentry_exit_cond_resched <- NOP
+ *
+ * VOLUNTARY:
+ *   cond_resched               <- __cond_resched
+ *   might_resched              <- __cond_resched
+ *   preempt_schedule           <- NOP
+ *   preempt_schedule_notrace   <- NOP
+ *   irqentry_exit_cond_resched <- NOP
+ *
+ * FULL:
+ *   cond_resched               <- RET0
+ *   might_resched              <- RET0
+ *   preempt_schedule           <- preempt_schedule
+ *   preempt_schedule_notrace   <- preempt_schedule_notrace
+ *   irqentry_exit_cond_resched <- irqentry_exit_cond_resched
+ */
+
+enum {
+       preempt_dynamic_undefined = -1,
+       preempt_dynamic_none,
+       preempt_dynamic_voluntary,
+       preempt_dynamic_full,
+};
+
+int preempt_dynamic_mode = preempt_dynamic_undefined;
+
+int sched_dynamic_mode(const char *str)
+{
+       if (!strcmp(str, "none"))
+               return preempt_dynamic_none;
+
+       if (!strcmp(str, "voluntary"))
+               return preempt_dynamic_voluntary;
+
+       if (!strcmp(str, "full"))
+               return preempt_dynamic_full;
+
+       return -EINVAL;
+}
+
+void sched_dynamic_update(int mode)
+{
+       /*
+        * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
+        * the ZERO state, which is invalid.
+        */
+       static_call_update(cond_resched, __cond_resched);
+       static_call_update(might_resched, __cond_resched);
+       static_call_update(preempt_schedule, __preempt_schedule_func);
+       static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
+       static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+
+       switch (mode) {
+       case preempt_dynamic_none:
+               static_call_update(cond_resched, __cond_resched);
+               static_call_update(might_resched, (void *)&__static_call_return0);
+               static_call_update(preempt_schedule, NULL);
+               static_call_update(preempt_schedule_notrace, NULL);
+               static_call_update(irqentry_exit_cond_resched, NULL);
+               pr_info("Dynamic Preempt: none\n");
+               break;
+
+       case preempt_dynamic_voluntary:
+               static_call_update(cond_resched, __cond_resched);
+               static_call_update(might_resched, __cond_resched);
+               static_call_update(preempt_schedule, NULL);
+               static_call_update(preempt_schedule_notrace, NULL);
+               static_call_update(irqentry_exit_cond_resched, NULL);
+               pr_info("Dynamic Preempt: voluntary\n");
+               break;
+
+       case preempt_dynamic_full:
+               static_call_update(cond_resched, (void *)&__static_call_return0);
+               static_call_update(might_resched, (void *)&__static_call_return0);
+               static_call_update(preempt_schedule, __preempt_schedule_func);
+               static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
+               static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
+               pr_info("Dynamic Preempt: full\n");
+               break;
+       }
+
+       preempt_dynamic_mode = mode;
+}
+
+static int __init setup_preempt_mode(char *str)
+{
+       int mode = sched_dynamic_mode(str);
+       if (mode < 0) {
+               pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);
+               return 0;
+       }
+
+       sched_dynamic_update(mode);
+       return 1;
+}
+__setup("preempt=", setup_preempt_mode);
+
+static void __init preempt_dynamic_init(void)
+{
+       if (preempt_dynamic_mode == preempt_dynamic_undefined) {
+               if (IS_ENABLED(CONFIG_PREEMPT_NONE)) {
+                       sched_dynamic_update(preempt_dynamic_none);
+               } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) {
+                       sched_dynamic_update(preempt_dynamic_voluntary);
+               } else {
+                       /* Default static call setting, nothing to do */
+                       WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT));
+                       preempt_dynamic_mode = preempt_dynamic_full;
+                       pr_info("Dynamic Preempt: full\n");
+               }
+       }
+}
+
+#else /* !CONFIG_PREEMPT_DYNAMIC */
+
+static inline void preempt_dynamic_init(void) { }
+
+#endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */
+
 /**
  * yield - yield the current processor to other threads.
  *