linux-kernel - [PATCH 1/3] sched: Add switch_mm_irqs

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Date:	Thu, 21 Apr 2016 10:57:28 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 1/3] sched: Add switch_mm_irqs_off and use it in the scheduler

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

Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 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