With an RCU based mmu_notifier implementation, any callout to mmu_notifier_invalidate_range_start, mmu_notifier_invalidate_range_end,
or mmu_notifier_invalidate_page would not be allowed to call schedule as that could potentially allow a modification to the mmu_notifier structure while it is currently being used.
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Robin Holt <holt@xxxxxxx>
---
include/linux/mmu_notifier.h | 3 ++
mm/mmu_notifier.c | 70 +++++++++++++++++++++++++----------------
2 files changed, 46 insertions(+), 27 deletions(-)
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 1d1b1e1..23c3c86 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -4,6 +4,7 @@
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/mm_types.h>
+#include <linux/srcu.h>
struct mmu_notifier;
struct mmu_notifier_ops;
@@ -19,6 +20,8 @@ struct mmu_notifier_ops;
struct mmu_notifier_mm {
/* all mmu notifiers registerd in this mm are queued in this list */
struct hlist_head list;
+ /* srcu structure for this mm */
+ struct srcu_struct srcu;
/* to serialize the list modifications and hlist_unhashed */
spinlock_t lock;
};
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 9a611d3..10703ca 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -14,6 +14,7 @@
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/err.h>
+#include <linux/srcu.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/slab.h>
@@ -25,14 +26,15 @@
* in parallel despite there being no task using this mm any more,
* through the vmas outside of the exit_mmap context, such as with
* vmtruncate. This serializes against mmu_notifier_unregister with
- * the mmu_notifier_mm->lock in addition to RCU and it serializes
- * against the other mmu notifiers with RCU. struct mmu_notifier_mm
+ * the mmu_notifier_mm->lock in addition to SRCU and it serializes
+ * against the other mmu notifiers with SRCU. struct mmu_notifier_mm
* can't go away from under us as exit_mmap holds an mm_count pin
* itself.
*/
void __mmu_notifier_release(struct mm_struct *mm)
{
struct mmu_notifier *mn;
+ int srcu;
spin_lock(&mm->mmu_notifier_mm->lock);
while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
@@ -47,10 +49,10 @@ void __mmu_notifier_release(struct mm_struct *mm)
*/
hlist_del_init_rcu(&mn->hlist);
/*
- * RCU here will block mmu_notifier_unregister until
+ * SRCU here will block mmu_notifier_unregister until
* ->release returns.
*/
- rcu_read_lock();
+ srcu = srcu_read_lock(&mm->mmu_notifier_mm->srcu);
spin_unlock(&mm->mmu_notifier_mm->lock);
/*
* if ->release runs before mmu_notifier_unregister it
@@ -61,13 +63,13 @@ void __mmu_notifier_release(struct mm_struct *mm)
*/
if (mn->ops->release)
mn->ops->release(mn, mm);
- rcu_read_unlock();
+ srcu_read_unlock(&mm->mmu_notifier_mm->srcu, srcu);
spin_lock(&mm->mmu_notifier_mm->lock);
}
spin_unlock(&mm->mmu_notifier_mm->lock);
/*
- * synchronize_rcu here prevents mmu_notifier_release to
+ * synchronize_srcu here prevents mmu_notifier_release to
* return to exit_mmap (which would proceed freeing all pages
* in the mm) until the ->release method returns, if it was
* invoked by mmu_notifier_unregister.
@@ -75,7 +77,7 @@ void __mmu_notifier_release(struct mm_struct *mm)
* The mmu_notifier_mm can't go away from under us because one
* mm_count is hold by exit_mmap.
*/
- synchronize_rcu();
+ synchronize_srcu(&mm->mmu_notifier_mm->srcu);
}
/*
@@ -88,14 +90,14 @@ int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
{
struct mmu_notifier *mn;
struct hlist_node *n;
- int young = 0;
+ int young = 0, srcu;
- rcu_read_lock();
+ srcu = srcu_read_lock(&mm->mmu_notifier_mm->srcu);
hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->clear_flush_young)
young |= mn->ops->clear_flush_young(mn, mm, address);
}
- rcu_read_unlock();
+ srcu_read_unlock(&mm->mmu_notifier_mm->srcu, srcu);
return young;
}
@@ -105,9 +107,9 @@ int __mmu_notifier_test_young(struct mm_struct *mm,
{
struct mmu_notifier *mn;
struct hlist_node *n;
- int young = 0;
+ int young = 0, srcu;
- rcu_read_lock();
+ srcu = srcu_read_lock(&mm->mmu_notifier_mm->srcu);
hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->test_young) {
young = mn->ops->test_young(mn, mm, address);
@@ -115,7 +117,7 @@ int __mmu_notifier_test_young(struct mm_struct *mm,
break;
}
}
- rcu_read_unlock();
+ srcu_read_unlock(&mm->mmu_notifier_mm->srcu, srcu);
return young;
}
@@ -125,8 +127,9 @@ void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
{
struct mmu_notifier *mn;
struct hlist_node *n;
+ int srcu;
- rcu_read_lock();
+ srcu = srcu_read_lock(&mm->mmu_notifier_mm->srcu);
hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->change_pte)
mn->ops->change_pte(mn, mm, address, pte);
@@ -137,7 +140,7 @@ void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
else if (mn->ops->invalidate_page)
mn->ops->invalidate_page(mn, mm, address);
}
- rcu_read_unlock();
+ srcu_read_unlock(&mm->mmu_notifier_mm->srcu, srcu);
}
void __mmu_notifier_invalidate_page(struct mm_struct *mm,
@@ -145,13 +148,14 @@ void __mmu_notifier_invalidate_page(struct mm_struct *mm,
{
struct mmu_notifier *mn;
struct hlist_node *n;
+ int srcu;
- rcu_read_lock();
+ srcu = srcu_read_lock(&mm->mmu_notifier_mm->srcu);
hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->invalidate_page)
mn->ops->invalidate_page(mn, mm, address);
}
- rcu_read_unlock();
+ srcu_read_unlock(&mm->mmu_notifier_mm->srcu, srcu);
}
void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
@@ -159,13 +163,14 @@ void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
{
struct mmu_notifier *mn;
struct hlist_node *n;
+ int srcu;
- rcu_read_lock();
+ srcu = srcu_read_lock(&mm->mmu_notifier_mm->srcu);
hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->invalidate_range_start)
mn->ops->invalidate_range_start(mn, mm, start, end);
}
- rcu_read_unlock();
+ srcu_read_unlock(&mm->mmu_notifier_mm->srcu, srcu);
}
void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
@@ -173,13 +178,14 @@ void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
{
struct mmu_notifier *mn;
struct hlist_node *n;
+ int srcu;
- rcu_read_lock();
+ srcu = srcu_read_lock(&mm->mmu_notifier_mm->srcu);
hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->invalidate_range_end)
mn->ops->invalidate_range_end(mn, mm, start, end);
}
- rcu_read_unlock();
+ srcu_read_unlock(&mm->mmu_notifier_mm->srcu, srcu);
}
static int do_mmu_notifier_register(struct mmu_notifier *mn,
@@ -196,6 +202,10 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn,
if (unlikely(!mmu_notifier_mm))
goto out;
+ ret = init_srcu_struct(&mmu_notifier_mm->srcu);
+ if (unlikely(ret))
+ goto out_kfree;
+
if (take_mmap_sem)
down_write(&mm->mmap_sem);
ret = mm_take_all_locks(mm);
@@ -226,6 +236,9 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn,
out_cleanup:
if (take_mmap_sem)
up_write(&mm->mmap_sem);
+ if (mmu_notifier_mm)
+ cleanup_srcu_struct(&mmu_notifier_mm->srcu);
+out_kfree:
/* kfree() does nothing if mmu_notifier_mm is NULL */
kfree(mmu_notifier_mm);
out:
@@ -266,6 +279,7 @@ EXPORT_SYMBOL_GPL(__mmu_notifier_register);
void __mmu_notifier_mm_destroy(struct mm_struct *mm)
{
BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
+ cleanup_srcu_struct(&mm->mmu_notifier_mm->srcu);
kfree(mm->mmu_notifier_mm);
mm->mmu_notifier_mm = LIST_POISON1; /* debug */
}
@@ -273,8 +287,8 @@ void __mmu_notifier_mm_destroy(struct mm_struct *mm)
/*
* This releases the mm_count pin automatically and frees the mm
* structure if it was the last user of it. It serializes against
- * running mmu notifiers with RCU and against mmu_notifier_unregister
- * with the unregister lock + RCU. All sptes must be dropped before
+ * running mmu notifiers with SRCU and against mmu_notifier_unregister
+ * with the unregister lock + SRCU. All sptes must be dropped before
* calling mmu_notifier_unregister. ->release or any other notifier
* method may be invoked concurrently with mmu_notifier_unregister,
* and only after mmu_notifier_unregister returned we're guaranteed
@@ -286,13 +300,15 @@ void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
spin_lock(&mm->mmu_notifier_mm->lock);
if (!hlist_unhashed(&mn->hlist)) {
+ int srcu;
+
hlist_del_rcu(&mn->hlist);
/*
- * RCU here will force exit_mmap to wait ->release to finish
+ * SRCU here will force exit_mmap to wait ->release to finish
* before freeing the pages.
*/
- rcu_read_lock();
+ srcu = srcu_read_lock(&mm->mmu_notifier_mm->srcu);
spin_unlock(&mm->mmu_notifier_mm->lock);
/*
* exit_mmap will block in mmu_notifier_release to
@@ -301,7 +317,7 @@ void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
*/
if (mn->ops->release)
mn->ops->release(mn, mm);
- rcu_read_unlock();
+ srcu_read_unlock(&mm->mmu_notifier_mm->srcu, srcu);
} else
spin_unlock(&mm->mmu_notifier_mm->lock);
@@ -309,7 +325,7 @@ void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
* Wait any running method to finish, of course including
* ->release if it was run by mmu_notifier_relase instead of us.
*/
- synchronize_rcu();
+ synchronize_srcu(&mm->mmu_notifier_mm->srcu);
BUG_ON(atomic_read(&mm->mm_count) <= 0);
--
1.7.8.2
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