diff --git a/include/linux/futex.h b/include/linux/futex.h
index 18ed18d5cbc1..a895d8c69d66 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -23,28 +23,32 @@ struct task_struct;
  *  01 : Shared futex (PTHREAD_PROCESS_SHARED)
  *	mapped on a file (reference on the underlying inode)
  *  10 : Shared futex (PTHREAD_PROCESS_SHARED)
- *       (but private mapping on an mm, and reference taken on it)
+ *       (but private mapping on an mm)
 */
 
-#define FUT_OFF_INODE    1 /* We set bit 0 if key has a reference on inode */
-#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
+#define FUT_OFF_INODE    1 /* We set bit 0 if shared key identifies an inode */
+#define FUT_OFF_MMSHARED 2 /* We set bit 1 if shared key identifies an mm */
 
 union futex_key {
+	/* For FUT_OFF_INODE */
 	struct {
 		u64 i_seq;
 		unsigned long pgoff;
 		unsigned int offset;
 		/* unsigned int node; */
 	} shared;
+
+	/* For FUT_OFF_MMSHARED or private */
 	struct {
 		union {
-			struct mm_struct *mm;
-			u64 __tmp;
+			struct mm_struct *mm; /* for private */
+			u64 mm_seq; /* for FUT_OFF_MMSHARED */
 		};
 		unsigned long address;
 		unsigned int offset;
 		/* unsigned int node; */
 	} private;
+
 	struct {
 		u64 ptr;
 		unsigned long word;
@@ -152,11 +156,10 @@ static inline void futex_set_vdso_cs_range(struct futex_mm_data *fd, unsigned in
 static inline void futex_fixup_robust_unlock(struct pt_regs *regs) { }
 #endif /* !CONFIG_FUTEX_ROBUST_UNLOCK */
 
-
-#if defined(CONFIG_FUTEX_PRIVATE_HASH) || defined(CONFIG_FUTEX_ROBUST_UNLOCK)
+#ifdef CONFIG_FUTEX
 void futex_mm_init(struct mm_struct *mm);
 #else
 static inline void futex_mm_init(struct mm_struct *mm) { }
-#endif
+#endif /* !CONFIG_FUTEX */
 
 #endif /* _LINUX_FUTEX_H */
diff --git a/include/linux/futex_types.h b/include/linux/futex_types.h
index d320c0571f0c..34b16f2828e7 100644
--- a/include/linux/futex_types.h
+++ b/include/linux/futex_types.h
@@ -85,10 +85,12 @@ struct futex_unlock_cs_ranges { };
  * struct futex_mm_data - Futex related per MM data
  * @phash:	Futex private hash related data
  * @unlock:	Futex unlock VDSO critical sections
+ * @unique_id:	Unique ID of the MM, for FUT_OFF_MMSHARED futexes
  */
 struct futex_mm_data {
 	struct futex_mm_phash		phash;
 	struct futex_unlock_cs_ranges	unlock;
+	atomic64_t			unique_id;
 };
 #else  /* CONFIG_FUTEX */
 struct futex_sched_data { };
diff --git a/include/linux/irq-entry-common.h b/include/linux/irq-entry-common.h
index 0bb6c03481fa..c74b5c87e10f 100644
--- a/include/linux/irq-entry-common.h
+++ b/include/linux/irq-entry-common.h
@@ -468,6 +468,25 @@ static inline void irqentry_exit_to_kernel_mode_preempt(struct pt_regs *regs,
 		irqentry_exit_cond_resched();
 }
 
+/*
+ * The deferred hrtimer rearm is the tail of the timer interrupt, moved to the
+ * interrupt return path so that it runs after a possible reschedule. By now
+ * irq_exit_rcu() has left lockdep's hardirq context. Re-enter it for the
+ * rearm, so that the hrtimer base lock and the timekeeping sequence count are
+ * not chained onto the locks held by the interrupted context, which would add
+ * new lock chains for every lock stack an interrupt hits.
+ *
+ * The rearm on return to user mode needs no such annotation: no locks are
+ * held there, so it uses the same lock chains as the rearm in hardirq
+ * context.
+ */
+static __always_inline void irqentry_hrtimer_rearm_deferred(void)
+{
+	lockdep_hardirq_enter();
+	hrtimer_rearm_deferred();
+	lockdep_hardirq_exit();
+}
+
 /**
  * irqentry_exit_to_kernel_mode_after_preempt - Establish trace, lockdep and RCU state
  * @regs:	Pointer to current's pt_regs
@@ -491,7 +510,7 @@ irqentry_exit_to_kernel_mode_after_preempt(struct pt_regs *regs, irqentry_state_
 		 */
 		if (state.exit_rcu) {
 			instrumentation_begin();
-			hrtimer_rearm_deferred();
+			irqentry_hrtimer_rearm_deferred();
 			/* Tell the tracer that IRET will enable interrupts */
 			trace_hardirqs_on_prepare();
 			lockdep_hardirqs_on_prepare();
@@ -502,7 +521,7 @@ irqentry_exit_to_kernel_mode_after_preempt(struct pt_regs *regs, irqentry_state_
 		}
 
 		instrumentation_begin();
-		hrtimer_rearm_deferred();
+		irqentry_hrtimer_rearm_deferred();
 		/* Covers both tracing and lockdep */
 		trace_hardirqs_on();
 		instrumentation_end();
diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index 095f9fe440e3..a240638f69e5 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -439,12 +439,35 @@ struct hrtimer_sleeper *futex_setup_timer(ktime_t *time, struct hrtimer_sleeper
 }
 
 /*
- * Generate a machine wide unique identifier for this inode.
+ * Generate a machine wide unique identifier for this object (inode or mm).
  *
  * This relies on u64 not wrapping in the life-time of the machine; which with
  * 1ns resolution means almost 585 years.
- *
- * This further relies on the fact that a well formed program will not unmap
+ */
+static u64 get_object_id(atomic64_t *object_seq)
+{
+	static atomic64_t last_assigned_seq;
+	u64 old;
+
+	/* Does the object already have a sequence number? */
+	old = atomic64_read(object_seq);
+	if (likely(old))
+		return old;
+
+	for (;;) {
+		u64 new = atomic64_inc_return(&last_assigned_seq);
+		if (WARN_ON_ONCE(!new))
+			continue;
+
+		old = 0;
+		if (!atomic64_try_cmpxchg_relaxed(object_seq, &old, new))
+			return old;
+		return new;
+	}
+}
+
+/*
+ * This relies on the fact that a well formed program will not unmap
  * the file while it has a (shared) futex waiting on it. This mapping will have
  * a file reference which pins the mount and inode.
  *
@@ -458,24 +481,7 @@ struct hrtimer_sleeper *futex_setup_timer(ktime_t *time, struct hrtimer_sleeper
  */
 static u64 get_inode_sequence_number(struct inode *inode)
 {
-	static atomic64_t i_seq;
-	u64 old;
-
-	/* Does the inode already have a sequence number? */
-	old = atomic64_read(&inode->i_sequence);
-	if (likely(old))
-		return old;
-
-	for (;;) {
-		u64 new = atomic64_inc_return(&i_seq);
-		if (WARN_ON_ONCE(!new))
-			continue;
-
-		old = 0;
-		if (!atomic64_try_cmpxchg_relaxed(&inode->i_sequence, &old, new))
-			return old;
-		return new;
-	}
+	return get_object_id(&inode->i_sequence);
 }
 
 /**
@@ -683,8 +689,8 @@ int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key,
 			goto out;
 		}
 
-		key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
-		key->private.mm = mm;
+		key->both.offset |= FUT_OFF_MMSHARED;
+		key->private.mm_seq = get_object_id(&mm->futex.unique_id);
 		key->private.address = address;
 
 	} else {
@@ -2055,13 +2061,12 @@ static void futex_robust_unlock_init_mm(struct futex_mm_data *fd)
 static inline void futex_robust_unlock_init_mm(struct futex_mm_data *fd) { }
 #endif /* !CONFIG_FUTEX_ROBUST_UNLOCK */
 
-#if defined(CONFIG_FUTEX_PRIVATE_HASH) || defined(CONFIG_FUTEX_ROBUST_UNLOCK)
 void futex_mm_init(struct mm_struct *mm)
 {
+	atomic64_set(&mm->futex.unique_id, 0);
 	futex_hash_init_mm(&mm->futex);
 	futex_robust_unlock_init_mm(&mm->futex);
 }
-#endif
 
 int futex_hash_prctl(unsigned long arg2, unsigned long arg3, unsigned long arg4)
 {