[PATCH v3 1/7] sched/preempt: move PREEMPT_DYNAMIC logic later

Mark Rutland
2022-02-09T15:38:53Z

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>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
---
kernel/sched/core.c | 272 ++++++++++++++++++++++----------------------
1 file changed, 136 insertions(+), 136 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 848eaa0efe0e..6e8998267102 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6553,142 +6553,6 @@ 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.
@@ -8263,6 +8127,142 @@ 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.
*
--
2.30.2