[PATCH] sched/mm: call finish_arch_post_lock_switch in idle_task_exitand use_mm

[Martin Schwidefsky]

The finish_arch_post_lock_switch is called at the end of the task
switch after all locks have been released. In concept it is paired
with the switch_mm function, but the current code only does the
call in finish_task_switch. Add the call to idle_task_exit and
use_mm. One use case for the additional calls is s390 which will
use finish_arch_post_lock_switch to wait for the completion of
TLB flush operations.

Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
 include/linux/mmu_context.h | 6 ++++++
 kernel/sched/core.c         | 6 ++++--
 kernel/sched/sched.h        | 3 ---
 mm/mmu_context.c            | 3 +--
 4 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/linux/mmu_context.h b/include/linux/mmu_context.h
index 70fffeb..38f5550 100644
--- a/include/linux/mmu_context.h
+++ b/include/linux/mmu_context.h
@@ -1,9 +1,15 @@
 #ifndef _LINUX_MMU_CONTEXT_H
 #define _LINUX_MMU_CONTEXT_H
 
+#include <asm/mmu_context.h>
+
 struct mm_struct;
 
 void use_mm(struct mm_struct *mm);
 void unuse_mm(struct mm_struct *mm);
 
+#ifndef finish_arch_post_lock_switch
+# define finish_arch_post_lock_switch()	do { } while (0)
+#endif
+
 #endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c180860..ffa234c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -32,7 +32,7 @@
 #include <linux/init.h>
 #include <linux/uaccess.h>
 #include <linux/highmem.h>
-#include <asm/mmu_context.h>
+#include <linux/mmu_context.h>
 #include <linux/interrupt.h>
 #include <linux/capability.h>
 #include <linux/completion.h>
@@ -4154,8 +4154,10 @@ void idle_task_exit(void)
 
 	BUG_ON(cpu_online(smp_processor_id()));
 
-	if (mm != &init_mm)
+	if (mm != &init_mm) {
 		switch_mm(mm, &init_mm, current);
+		finish_arch_post_lock_switch();
+	}
 	mmdrop(mm);
 }
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 88c85b2..ad48db3 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -850,9 +850,6 @@ static inline int task_running(struct rq *rq, struct task_struct *p)
 #ifndef finish_arch_switch
 # define finish_arch_switch(prev)	do { } while (0)
 #endif
-#ifndef finish_arch_post_lock_switch
-# define finish_arch_post_lock_switch()	do { } while (0)
-#endif
 
 #ifndef __ARCH_WANT_UNLOCKED_CTXSW
 static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
diff --git a/mm/mmu_context.c b/mm/mmu_context.c
index 8a8cd02..56ecbbd 100644
--- a/mm/mmu_context.c
+++ b/mm/mmu_context.c
@@ -8,8 +8,6 @@
 #include <linux/export.h>
 #include <linux/sched.h>
 
-#include <asm/mmu_context.h>
-
 /*
  * use_mm
  *	Makes the calling kernel thread take on the specified
@@ -31,6 +29,7 @@ void use_mm(struct mm_struct *mm)
 	tsk->mm = mm;
 	switch_mm(active_mm, mm, tsk);
 	task_unlock(tsk);
+	finish_arch_post_lock_switch();
 
 	if (active_mm != mm)
 		mmdrop(active_mm);
-- 
1.8.3.4

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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