[RFC v1 1/4] exit: add arch mmput hook in exit_mm

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

This simple patch adds a hook for the mmput in exit_mm. This allows
archs to perform the mmput in custom ways if desired (e.g.
asynchronously)

No functional change intended.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 include/asm-generic/mmu_context.h | 4 ++++
 kernel/exit.c                     | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/mmu_context.h b/include/asm-generic/mmu_context.h
index 91727065bacb..900931a6a105 100644
--- a/include/asm-generic/mmu_context.h
+++ b/include/asm-generic/mmu_context.h
@@ -73,4 +73,8 @@ static inline void deactivate_mm(struct task_struct *tsk,
 }
 #endif
 
+#ifndef arch_exit_mm_mmput
+#define arch_exit_mm_mmput mmput
+#endif
+
 #endif /* __ASM_GENERIC_MMU_CONTEXT_H */
diff --git a/kernel/exit.c b/kernel/exit.c
index f702a6a63686..6eb1fdcc434e 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -504,7 +504,7 @@ static void exit_mm(void)
 	task_unlock(current);
 	mmap_read_unlock(mm);
 	mm_update_next_owner(mm);
-	mmput(mm);
+	arch_exit_mm_mmput(mm);
 	if (test_thread_flag(TIF_MEMDIE))
 		exit_oom_victim();
 }
-- 
2.31.1