From 6a90a83f1d1957647581ca48caa1f7cc4fa44f8d Mon Sep 17 00:00:00 2001
From: Sean Christopherson <sean.j.christopherson@intel.com>
Date: Fri, 28 Dec 2018 00:33:28 -0800
Subject: [PATCH] mm/mmu_notifier.c: remove mmu_notifier_synchronize()
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Contrary to its name, mmu_notifier_synchronize() does not synchronize the
notifier's SRCU instance, but rather waits for RCU callbacks to finish.
i.e. it invokes rcu_barrier(). The RCU documentation is quite clear on
this matter, explicitly calling out that rcu_barrier() does not imply
synchronize_rcu().
As there are no callers of mmu_notifier_synchronize() and it's unclear
whether any user of mmu_notifier_call_srcu() will ever want to barrier on
their callbacks, simply remove the function.
Link: http://lkml.kernel.org/r/20181106134705.14197-1-sean.j.christopherson@intel.com
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: J茅r么me Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/mmu_notifier.h | 1 -
mm/mmu_notifier.c | 7 -------
2 files changed, 8 deletions(-)
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 9893a6432adf..913c3c13e36e 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -420,7 +420,6 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
void (*func)(struct rcu_head *rcu));
-extern void mmu_notifier_synchronize(void);
#else /* CONFIG_MMU_NOTIFIER */
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 5119ff846769..755466cd289a 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -35,13 +35,6 @@ void mmu_notifier_call_srcu(struct rcu_head *rcu,
}
EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu);
-void mmu_notifier_synchronize(void)
-{
- /* Wait for any running method to finish. */
- srcu_barrier(&srcu);
-}
-EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);
-
/*
* This function can't run concurrently against mmu_notifier_register
* because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
--
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