ARM: OMAP3: PM: remove access to PRM_VOLTCTRL register

[pandora-kernel.git] / mm / mmu_notifier.c

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 8d1ca2d..a160ec8 100644 (file)
--- 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 *n;
        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, n, &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);