From: Ingo Molnar <mingo@kernel.org>
Date: Sat, 25 Jan 2020 09:05:23 +0000 (+0100)
Subject: Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck... 
X-Git-Tag: v5.6-rc1~171^2
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=f8a4bb6bfa639fbdd07aede615be6dffe86a9713;p=linux.git

Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull RCU updates from Paul E. McKenney:

 - Expedited grace-period updates
 - kfree_rcu() updates
 - RCU list updates
 - Preemptible RCU updates
 - Torture-test updates
 - Miscellaneous fixes
 - Documentation updates

Signed-off-by: Ingo Molnar <mingo@kernel.org>
---

f8a4bb6bfa639fbdd07aede615be6dffe86a9713
diff --cc include/linux/rculist_nulls.h
index 61974c4c566b,409a86bb5f25..e5b752027a03
--- a/include/linux/rculist_nulls.h
+++ b/include/linux/rculist_nulls.h
@@@ -94,49 -102,12 +102,49 @@@ static inline void hlist_nulls_add_head
  	struct hlist_nulls_node *first = h->first;
  
  	n->next = first;
- 	n->pprev = &h->first;
+ 	WRITE_ONCE(n->pprev, &h->first);
  	rcu_assign_pointer(hlist_nulls_first_rcu(h), n);
  	if (!is_a_nulls(first))
- 		first->pprev = &n->next;
+ 		WRITE_ONCE(first->pprev, &n->next);
  }
  
 +/**
 + * hlist_nulls_add_tail_rcu
 + * @n: the element to add to the hash list.
 + * @h: the list to add to.
 + *
 + * Description:
 + * Adds the specified element to the specified hlist_nulls,
 + * while permitting racing traversals.
 + *
 + * The caller must take whatever precautions are necessary
 + * (such as holding appropriate locks) to avoid racing
 + * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
 + * or hlist_nulls_del_rcu(), running on this same list.
 + * However, it is perfectly legal to run concurrently with
 + * the _rcu list-traversal primitives, such as
 + * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency
 + * problems on Alpha CPUs.  Regardless of the type of CPU, the
 + * list-traversal primitive must be guarded by rcu_read_lock().
 + */
 +static inline void hlist_nulls_add_tail_rcu(struct hlist_nulls_node *n,
 +					    struct hlist_nulls_head *h)
 +{
 +	struct hlist_nulls_node *i, *last = NULL;
 +
 +	/* Note: write side code, so rcu accessors are not needed. */
 +	for (i = h->first; !is_a_nulls(i); i = i->next)
 +		last = i;
 +
 +	if (last) {
 +		n->next = last->next;
 +		n->pprev = &last->next;
 +		rcu_assign_pointer(hlist_next_rcu(last), n);
 +	} else {
 +		hlist_nulls_add_head_rcu(n, h);
 +	}
 +}
 +
  /**
   * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type
   * @tpos:	the type * to use as a loop cursor.