Commit 6a90a83f authored Dec 28, 2018 by Sean Christopherson Committed by Linus Torvalds Dec 28, 2018

mm/mmu_notifier.c: remove mmu_notifier_synchronize()

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: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 5eb570a8

include/linux/mmu_notifier.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -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 */

mm/mmu_notifier.c

+0 −7

Original line number	Diff line number	Diff line
		@@ -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

Admin message