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Diffstat (limited to 'mm')
-rw-r--r--mm/mmu_notifier.c80
1 files changed, 40 insertions, 40 deletions
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 8d1ca2de4080..c1f947b4f61d 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -37,51 +37,48 @@ static struct srcu_struct srcu;
void __mmu_notifier_release(struct mm_struct *mm)
{
struct mmu_notifier *mn;
+ struct hlist_node *node;
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, node, &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);
}
@@ -302,31 +299,34 @@ 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);