Merge tag 'asoc-v3.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

ASoC: Updates for v3.10

A series of driver specific updates, none particularly critical, plus
one fix to the compressed API code to handle capture streams properly
which is very safe for mainline as there's no current users.

1 files changed, 39 insertions, 40 deletions

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index be04122..6725ff1 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -40,48 +40,44 @@ void __mmu_notifier_release(struct mm_struct *mm)
 	int id;
 
 	/*
-	 * srcu_read_lock() here will block synchronize_srcu() in
-	 * mmu_notifier_unregister() until all registered
-	 * ->release() callouts this function makes have
-	 * returned.
+	 * SRCU here will block mmu_notifier_unregister until
+	 * ->release returns.
 	 */
 	id = srcu_read_lock(&srcu);
+	hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist)
+		/*
+		 * If ->release runs before mmu_notifier_unregister it must be
+		 * handled, as it's the only way for the driver to flush all
+		 * existing sptes and stop the driver from establishing any more
+		 * sptes before all the pages in the mm are freed.
+		 */
+		if (mn->ops->release)
+			mn->ops->release(mn, mm);
+	srcu_read_unlock(&srcu, id);
+
 	spin_lock(&mm->mmu_notifier_mm->lock);
 	while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
 		mn = hlist_entry(mm->mmu_notifier_mm->list.first,
 				 struct mmu_notifier,
 				 hlist);
-
 		/*
-		 * Unlink.  This will prevent mmu_notifier_unregister()
-		 * from also making the ->release() callout.
+		 * We arrived before mmu_notifier_unregister so
+		 * mmu_notifier_unregister will do nothing other than to wait
+		 * for ->release to finish and for mmu_notifier_unregister to
+		 * return.
 		 */
 		hlist_del_init_rcu(&mn->hlist);
-		spin_unlock(&mm->mmu_notifier_mm->lock);
-
-		/*
-		 * Clear sptes. (see 'release' description in mmu_notifier.h)
-		 */
-		if (mn->ops->release)
-			mn->ops->release(mn, mm);
-
-		spin_lock(&mm->mmu_notifier_mm->lock);
 	}
 	spin_unlock(&mm->mmu_notifier_mm->lock);
 
 	/*
-	 * All callouts to ->release() which we have done are complete.
-	 * Allow synchronize_srcu() in mmu_notifier_unregister() to complete
-	 */
-	srcu_read_unlock(&srcu, id);
-
-	/*
-	 * mmu_notifier_unregister() may have unlinked a notifier and may
-	 * still be calling out to it.	Additionally, other notifiers
-	 * may have been active via vmtruncate() et. al. Block here
-	 * to ensure that all notifier callouts for this mm have been
-	 * completed and the sptes are really cleaned up before returning
-	 * to exit_mmap().
+	 * synchronize_srcu here prevents mmu_notifier_release from returning to
+	 * exit_mmap (which would proceed with freeing all pages in the mm)
+	 * until the ->release method returns, if it was invoked by
+	 * mmu_notifier_unregister.
+	 *
+	 * The mmu_notifier_mm can't go away from under us because one mm_count
+	 * is held by exit_mmap.
 	 */
 	synchronize_srcu(&srcu);
 }
@@ -292,31 +288,34 @@ void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
 {
 	BUG_ON(atomic_read(&mm->mm_count) <= 0);
 
-	spin_lock(&mm->mmu_notifier_mm->lock);
 	if (!hlist_unhashed(&mn->hlist)) {
+		/*
+		 * SRCU here will force exit_mmap to wait for ->release to
+		 * finish before freeing the pages.
+		 */
 		int id;
 
+		id = srcu_read_lock(&srcu);
 		/*
-		 * Ensure we synchronize up with __mmu_notifier_release().
+		 * exit_mmap will block in mmu_notifier_release to guarantee
+		 * that ->release is called before freeing the pages.
 		 */
-		id = srcu_read_lock(&srcu);
-
-		hlist_del_rcu(&mn->hlist);
-		spin_unlock(&mm->mmu_notifier_mm->lock);
-
 		if (mn->ops->release)
 			mn->ops->release(mn, mm);
+		srcu_read_unlock(&srcu, id);
 
+		spin_lock(&mm->mmu_notifier_mm->lock);
 		/*
-		 * Allow __mmu_notifier_release() to complete.
+		 * Can not use list_del_rcu() since __mmu_notifier_release
+		 * can delete it before we hold the lock.
 		 */
-		srcu_read_unlock(&srcu, id);
-	} else
+		hlist_del_init_rcu(&mn->hlist);
 		spin_unlock(&mm->mmu_notifier_mm->lock);
+	}
 
 	/*
-	 * Wait for any running method to finish, including ->release() if it
-	 * was run by __mmu_notifier_release() instead of us.
+	 * Wait for any running method to finish, of course including
+	 * ->release if it was run by mmu_notifier_relase instead of us.
 	 */
 	synchronize_srcu(&srcu);