sched: Have sched_class_highest define by vmlinux.lds.h

Now that the sched_class descriptors are defined by the linker script, and
this needs to be aware of the existance of stop_sched_class when SMP is
enabled or not, as it is used as the "highest" priority when defined. Move
the declaration of sched_class_highest to the same location in the linker
script that inserts stop_sched_class, and this will also make it easier to
see what should be defined as the highest class, as this linker script
location defines the priorities as well.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191219214558.682913590@goodmis.org

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 2186d7b..66fb84c 100644 (file)
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -114,11 +114,14 @@
  * relation to each other.
  */
 #define SCHED_DATA                             \
+       STRUCT_ALIGN();                         \
+       __begin_sched_classes = .;              \
        *(__idle_sched_class)                   \
        *(__fair_sched_class)                   \
        *(__rt_sched_class)                     \
        *(__dl_sched_class)                     \
-       *(__stop_sched_class)
+       *(__stop_sched_class)                   \
+       __end_sched_classes = .;
 
 /*
  * Align to a 32 byte boundary equal to the

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0208b71..81640fe 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6646,6 +6646,14 @@ void __init sched_init(void)
        unsigned long ptr = 0;
        int i;
 
+       /* Make sure the linker didn't screw up */
+       BUG_ON(&idle_sched_class + 1 != &fair_sched_class ||
+              &fair_sched_class + 1 != &rt_sched_class ||
+              &rt_sched_class + 1   != &dl_sched_class);
+#ifdef CONFIG_SMP
+       BUG_ON(&dl_sched_class + 1 != &stop_sched_class);
+#endif
+
        wait_bit_init();
 
 #ifdef CONFIG_FAIR_GROUP_SCHED

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3368876..4165c06 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1811,7 +1811,7 @@ struct sched_class {
 #ifdef CONFIG_FAIR_GROUP_SCHED
        void (*task_change_group)(struct task_struct *p, int type);
 #endif
-};
+} __aligned(32); /* STRUCT_ALIGN(), vmlinux.lds.h */
 
 static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
 {
@@ -1825,17 +1825,18 @@ static inline void set_next_task(struct rq *rq, struct task_struct *next)
        next->sched_class->set_next_task(rq, next, false);
 }
 
-#ifdef CONFIG_SMP
-#define sched_class_highest (&stop_sched_class)
-#else
-#define sched_class_highest (&dl_sched_class)
-#endif
+/* Defined in include/asm-generic/vmlinux.lds.h */
+extern struct sched_class __begin_sched_classes[];
+extern struct sched_class __end_sched_classes[];
+
+#define sched_class_highest (__end_sched_classes - 1)
+#define sched_class_lowest  (__begin_sched_classes - 1)
 
 #define for_class_range(class, _from, _to) \
-       for (class = (_from); class != (_to); class = class->next)
+       for (class = (_from); class != (_to); class--)
 
 #define for_each_class(class) \
-       for_class_range(class, sched_class_highest, NULL)
+       for_class_range(class, sched_class_highest, sched_class_lowest)
 
 extern const struct sched_class stop_sched_class;
 extern const struct sched_class dl_sched_class;