[tip:sched/core] sched/core: Add switch_mm_irqs_off() and use it in the scheduler

[tip-bot for Andy Lutomirski <tipbot@zytor.com>]

Commit-ID:  f98db6013c557c216da5038d9c52045be55cd039
Gitweb:     http://git.kernel.org/tip/f98db6013c557c216da5038d9c52045be55cd039
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Tue, 26 Apr 2016 09:39:06 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 28 Apr 2016 11:44:19 +0200

sched/core: Add switch_mm_irqs_off() and use it in the scheduler

By default, this is the same thing as switch_mm().

x86 will override it as an optimization.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/df401df47bdd6be3e389c6f1e3f5310d70e81b2c.1461688545.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.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 70fffeb..a444178 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 9d84d60..adcafda 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>
@@ -2733,7 +2733,7 @@ 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;
@@ -5274,7 +5274,7 @@ 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);