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Subject[PATCH v2 2/8] sched: omit stop_sched_class when !SMP
Date
The stop class is invoked through stop_machine only.
This is dead code on UP builds.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
---
kernel/sched/Makefile | 4 ++--
kernel/sched/core.c | 60 +++++++++++++++++++++++++--------------------------
kernel/sched/sched.h | 4 ++++
3 files changed, 36 insertions(+), 32 deletions(-)

diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 89ab675866..5e4c2e7a63 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -16,9 +16,9 @@ CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
endif

obj-y += core.o loadavg.o clock.o cputime.o
-obj-y += idle_task.o fair.o rt.o deadline.o stop_task.o
+obj-y += idle_task.o fair.o rt.o deadline.o
obj-y += wait.o swait.o completion.o idle.o
-obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o
+obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o stop_task.o
obj-$(CONFIG_SCHED_AUTOGROUP) += autogroup.o
obj-$(CONFIG_SCHEDSTATS) += stats.o
obj-$(CONFIG_SCHED_DEBUG) += debug.o
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index de274b1bd2..94fa712791 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -788,36 +788,6 @@ void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
dequeue_task(rq, p, flags);
}

-void sched_set_stop_task(int cpu, struct task_struct *stop)
-{
- struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
- struct task_struct *old_stop = cpu_rq(cpu)->stop;
-
- if (stop) {
- /*
- * Make it appear like a SCHED_FIFO task, its something
- * userspace knows about and won't get confused about.
- *
- * Also, it will make PI more or less work without too
- * much confusion -- but then, stop work should not
- * rely on PI working anyway.
- */
- sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
-
- stop->sched_class = &stop_sched_class;
- }
-
- cpu_rq(cpu)->stop = stop;
-
- if (old_stop) {
- /*
- * Reset it back to a normal scheduling class so that
- * it can die in pieces.
- */
- old_stop->sched_class = &rt_sched_class;
- }
-}
-
/*
* __normal_prio - return the priority that is based on the static prio
*/
@@ -1588,6 +1558,36 @@ static void update_avg(u64 *avg, u64 sample)
*avg += diff >> 3;
}

+void sched_set_stop_task(int cpu, struct task_struct *stop)
+{
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
+ struct task_struct *old_stop = cpu_rq(cpu)->stop;
+
+ if (stop) {
+ /*
+ * Make it appear like a SCHED_FIFO task, its something
+ * userspace knows about and won't get confused about.
+ *
+ * Also, it will make PI more or less work without too
+ * much confusion -- but then, stop work should not
+ * rely on PI working anyway.
+ */
+ sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
+
+ stop->sched_class = &stop_sched_class;
+ }
+
+ cpu_rq(cpu)->stop = stop;
+
+ if (old_stop) {
+ /*
+ * Reset it back to a normal scheduling class so that
+ * it can die in pieces.
+ */
+ old_stop->sched_class = &rt_sched_class;
+ }
+}
+
#else

static inline int __set_cpus_allowed_ptr(struct task_struct *p,
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 6dda2aab73..053f60afb7 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1422,7 +1422,11 @@ static inline void set_curr_task(struct rq *rq, struct task_struct *curr)
curr->sched_class->set_curr_task(rq);
}

+#ifdef CONFIG_SMP
#define sched_class_highest (&stop_sched_class)
+#else
+#define sched_class_highest (&dl_sched_class)
+#endif
#define for_each_class(class) \
for (class = sched_class_highest; class; class = class->next)

--
2.9.4
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