The patch titled
Subject: mm/mmu_notifier.c: rename mmu_notifier_synchronize() to <...>_barrier()
has been added to the -mm tree. Its filename is
mm-mmu_notifier-rename-mmu_notifier_synchronize-to-_barrier.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-mmu_notifier-rename-mmu_notifier_synchronize-to-_barrier.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-mmu_notifier-rename-mmu_notifier_synchronize-to-_barrier.patch
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------------------------------------------------------
From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Subject: mm/mmu_notifier.c: rename mmu_notifier_synchronize() to <...>_barrier()
... and update its comment to explicitly reference its association with
mmu_notifier_call_srcu().
Contrary to its name, mmu_notifier_synchronize() does not synchronize the
notifier's SRCU instance, but rather waits for RCU callbacks to finishe,
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(). The misnomer could lean an unwary developer to
incorrectly assume that mmu_notifier_synchronize() can be used in
conjunction with mmu_notifier_unregister_no_release() to implement a
variation of mmu_notifier_unregister() that synchronizes SRCU without
invoking ->release. A Documentation-allergic and hasty developer could be
further confused by the fact that rcu_barrier() is indeed a pass-through
to synchronize_rcu()... in tiny SRCU.
Link: http://lkml.kernel.org/r/20181105192955.26305-1-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>
Cc: Oded Gabbay <oded.gabbay@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmu_notifier.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/mmu_notifier.c~mm-mmu_notifier-rename-mmu_notifier_synchronize-to-_barrier
+++ a/mm/mmu_notifier.c
@@ -35,12 +35,12 @@ void mmu_notifier_call_srcu(struct rcu_h
}
EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu);
-void mmu_notifier_synchronize(void)
+void mmu_notifier_barrier(void)
{
- /* Wait for any running method to finish. */
+ /* Wait for any running RCU callbacks (see above) to finish. */
srcu_barrier(&srcu);
}
-EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);
+EXPORT_SYMBOL_GPL(mmu_notifier_barrier);
/*
* This function can't run concurrently against mmu_notifier_register
_
Patches currently in -mm which might be from sean.j.christopherson@xxxxxxxxx are
mm-mmu_notifier-rename-mmu_notifier_synchronize-to-_barrier.patch
