Merge branches 'doc.2019.10.29a', 'fixes.2019.10.30a', 'nohz.2019.10.28a', 'replace.2019.10.30a', 'torture.2019.10.05a' and 'lkmm.2019.10.05a' into HEAD

doc.2019.10.29a: RCU documentation updates.
fixes.2019.10.30a: RCU miscellaneous fixes.
nohz.2019.10.28a: RCU NO_HZ and NO_HZ_FULL updates.
replace.2019.10.30a: Replace rcu_swap_protected() with rcu_replace().
torture.2019.10.05a: RCU torture-test updates.

lkmm.2019.10.05a: Linux kernel memory model updates.

Author: paulmckrcu

arch/x86/kvm/pmu.c

@@ -416,8 +416,8 @@ int kvm_vm_ioctl_set_pmu_event_filter(struct kvm *kvm, void __user *argp)
 	*filter = tmp;
 
 	mutex_lock(&kvm->lock);
-	rcu_swap_protected(kvm->arch.pmu_event_filter, filter,
-			   mutex_is_locked(&kvm->lock));
+	filter = rcu_replace_pointer(kvm->arch.pmu_event_filter, filter,
+				     mutex_is_locked(&kvm->lock));
 	mutex_unlock(&kvm->lock);
 
 	synchronize_srcu_expedited(&kvm->srcu);

drivers/gpu/drm/i915/gem/i915_gem_context.c

@@ -1629,7 +1629,7 @@ set_engines(struct i915_gem_context *ctx,
 		i915_gem_context_set_user_engines(ctx);
 	else
 		i915_gem_context_clear_user_engines(ctx);
-	rcu_swap_protected(ctx->engines, set.engines, 1);
+	set.engines = rcu_replace_pointer(ctx->engines, set.engines, 1);
 	mutex_unlock(&ctx->engines_mutex);
 
 	call_rcu(&set.engines->rcu, free_engines_rcu);

drivers/scsi/scsi.c

@@ -434,8 +434,8 @@ static void scsi_update_vpd_page(struct scsi_device *sdev, u8 page,
 		return;
 
 	mutex_lock(&sdev->inquiry_mutex);
-	rcu_swap_protected(*sdev_vpd_buf, vpd_buf,
-			   lockdep_is_held(&sdev->inquiry_mutex));
+	vpd_buf = rcu_replace_pointer(*sdev_vpd_buf, vpd_buf,
+				      lockdep_is_held(&sdev->inquiry_mutex));
 	mutex_unlock(&sdev->inquiry_mutex);
 
 	if (vpd_buf)

drivers/scsi/scsi_sysfs.c

@@ -466,10 +466,10 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 	sdev->request_queue = NULL;
 
 	mutex_lock(&sdev->inquiry_mutex);
-	rcu_swap_protected(sdev->vpd_pg80, vpd_pg80,
-			   lockdep_is_held(&sdev->inquiry_mutex));
-	rcu_swap_protected(sdev->vpd_pg83, vpd_pg83,
-			   lockdep_is_held(&sdev->inquiry_mutex));
+	vpd_pg80 = rcu_replace_pointer(sdev->vpd_pg80, vpd_pg80,
+				       lockdep_is_held(&sdev->inquiry_mutex));
+	vpd_pg83 = rcu_replace_pointer(sdev->vpd_pg83, vpd_pg83,
+				       lockdep_is_held(&sdev->inquiry_mutex));
 	mutex_unlock(&sdev->inquiry_mutex);
 
 	if (vpd_pg83)

fs/afs/vl_list.c

@@ -279,8 +279,8 @@ struct afs_vlserver_list *afs_extract_vlserver_list(struct afs_cell *cell,
 			struct afs_addr_list *old = addrs;
 
 			write_lock(&server->lock);
-			rcu_swap_protected(server->addresses, old,
-					   lockdep_is_held(&server->lock));
+			old = rcu_replace_pointer(server->addresses, old,
+						  lockdep_is_held(&server->lock));
 			write_unlock(&server->lock);
 			afs_put_addrlist(old);
 		}

include/linux/rculist_bl.h

@@ -24,34 +24,6 @@ static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
 		((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
 }
 
-/**
- * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
- * @n: the element to delete from the hash list.
- *
- * Note: hlist_bl_unhashed() on the node returns true after this. It is
- * useful for RCU based read lockfree traversal if the writer side
- * must know if the list entry is still hashed or already unhashed.
- *
- * In particular, it means that we can not poison the forward pointers
- * that may still be used for walking the hash list and we can only
- * zero the pprev pointer so list_unhashed() will return true after
- * this.
- *
- * The caller must take whatever precautions are necessary (such as
- * holding appropriate locks) to avoid racing with another
- * list-mutation primitive, such as hlist_bl_add_head_rcu() or
- * hlist_bl_del_rcu(), running on this same list.  However, it is
- * perfectly legal to run concurrently with the _rcu list-traversal
- * primitives, such as hlist_bl_for_each_entry_rcu().
- */
-static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n)
-{
-	if (!hlist_bl_unhashed(n)) {
-		__hlist_bl_del(n);
-		n->pprev = NULL;
-	}
-}
-
 /**
  * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
  * @n: the element to delete from the hash list.

include/linux/rcupdate.h

@@ -382,6 +382,24 @@ do {									      \
 		smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \
 } while (0)
 
+/**
+ * rcu_replace_pointer() - replace an RCU pointer, returning its old value
+ * @rcu_ptr: RCU pointer, whose old value is returned
+ * @ptr: regular pointer
+ * @c: the lockdep conditions under which the dereference will take place
+ *
+ * Perform a replacement, where @rcu_ptr is an RCU-annotated
+ * pointer and @c is the lockdep argument that is passed to the
+ * rcu_dereference_protected() call used to read that pointer.  The old
+ * value of @rcu_ptr is returned, and @rcu_ptr is set to @ptr.
+ */
+#define rcu_replace_pointer(rcu_ptr, ptr, c)				\
+({									\
+	typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c));	\
+	rcu_assign_pointer((rcu_ptr), (ptr));				\
+	__tmp;								\
+})
+
 /**
  * rcu_swap_protected() - swap an RCU and a regular pointer
  * @rcu_ptr: RCU pointer

include/linux/rcutiny.h

@@ -84,6 +84,7 @@ static inline void rcu_scheduler_starting(void) { }
 #endif /* #else #ifndef CONFIG_SRCU */
 static inline void rcu_end_inkernel_boot(void) { }
 static inline bool rcu_is_watching(void) { return true; }
+static inline void rcu_momentary_dyntick_idle(void) { }
 
 /* Avoid RCU read-side critical sections leaking across. */
 static inline void rcu_all_qs(void) { barrier(); }

include/linux/rcutree.h

@@ -37,6 +37,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func);
 
 void rcu_barrier(void);
 bool rcu_eqs_special_set(int cpu);
+void rcu_momentary_dyntick_idle(void);
 unsigned long get_state_synchronize_rcu(void);
 void cond_synchronize_rcu(unsigned long oldstate);
 

include/linux/tick.h

@@ -108,14 +108,16 @@ enum tick_dep_bits {
 	TICK_DEP_BIT_POSIX_TIMER	= 0,
 	TICK_DEP_BIT_PERF_EVENTS	= 1,
 	TICK_DEP_BIT_SCHED		= 2,
-	TICK_DEP_BIT_CLOCK_UNSTABLE	= 3
+	TICK_DEP_BIT_CLOCK_UNSTABLE	= 3,
+	TICK_DEP_BIT_RCU		= 4
 };
 
 #define TICK_DEP_MASK_NONE		0
 #define TICK_DEP_MASK_POSIX_TIMER	(1 << TICK_DEP_BIT_POSIX_TIMER)
 #define TICK_DEP_MASK_PERF_EVENTS	(1 << TICK_DEP_BIT_PERF_EVENTS)
 #define TICK_DEP_MASK_SCHED		(1 << TICK_DEP_BIT_SCHED)
 #define TICK_DEP_MASK_CLOCK_UNSTABLE	(1 << TICK_DEP_BIT_CLOCK_UNSTABLE)
+#define TICK_DEP_MASK_RCU		(1 << TICK_DEP_BIT_RCU)
 
 #ifdef CONFIG_NO_HZ_COMMON
 extern bool tick_nohz_enabled;
@@ -268,6 +270,9 @@ static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
 static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
 
+static inline void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) { }
+static inline void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { }
+
 static inline void tick_dep_set(enum tick_dep_bits bit) { }
 static inline void tick_dep_clear(enum tick_dep_bits bit) { }
 static inline void tick_dep_set_cpu(int cpu, enum tick_dep_bits bit) { }