[PATCH 1/3] sched: Add switch_mm_irqs_off and use it in the scheduler

From: Andy Lutomirski
Date: Thu Apr 21 2016 - 13:57:42 EST


By defailt, this is the same thing as switch_mm. x86 will override it
as an optimization.

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
include/linux/mmu_context.h | 7 +++++++
kernel/sched/core.c | 6 +++---
2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/linux/mmu_context.h b/include/linux/mmu_context.h
index 70fffeba7495..f9e09613c113 100644
--- a/include/linux/mmu_context.h
+++ b/include/linux/mmu_context.h
@@ -1,9 +1,16 @@
#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);

+/* Architectures that care about IRQ state in switch_mm can override this. */
+#ifndef switch_mm_irqs_off
+#define switch_mm_irqs_off switch_mm
+#endif
+
#endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d8465eeab8b3..3636abcafac0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -33,7 +33,7 @@
#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>
@@ -2712,7 +2712,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next);
} else
- switch_mm(oldmm, mm, next);
+ switch_mm_irqs_off(oldmm, mm, next);

if (!prev->mm) {
prev->active_mm = NULL;
@@ -5202,7 +5202,7 @@ void idle_task_exit(void)
BUG_ON(cpu_online(smp_processor_id()));

if (mm != &init_mm) {
- switch_mm(mm, &init_mm, current);
+ switch_mm_irqs_off(mm, &init_mm, current);
finish_arch_post_lock_switch();
}
mmdrop(mm);
--
2.5.5