From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> Subject: 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@xxxxxxxxx Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Jérôme Glisse <jglisse@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- --- a/include/linux/mmu_notifier.h~mm-mmu_notifier-remove-mmu_notifier_synchronize +++ a/include/linux/mmu_notifier.h @@ -420,7 +420,6 @@ static inline void mmu_notifier_mm_destr 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 */ --- a/mm/mmu_notifier.c~mm-mmu_notifier-remove-mmu_notifier_synchronize +++ a/mm/mmu_notifier.c @@ -35,13 +35,6 @@ void mmu_notifier_call_srcu(struct rcu_h } 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 _
