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Commit 6a90a83f authored by Sean Christopherson's avatar Sean Christopherson Committed by Linus Torvalds
Browse files

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: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus 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