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Subject[RFC PATCH 06/21] list: Remove superfluous WRITE_ONCE() from hlist_nulls implementation
Date
Commit 860c8802ace1 ("rcu: Use WRITE_ONCE() for assignments to ->pprev
for hlist_nulls") added WRITE_ONCE() invocations to hlist_nulls_add_head()
and hlist_nulls_del().

Since these functions should not ordinarily run concurrently with other
list accessors, restore the plain C assignments so that KCSAN can yell
if a data race occurs.

Cc: Eric Dumazet <edumazet@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
include/linux/list_nulls.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h
index fa51a801bf32..fd154ceb5b0d 100644
--- a/include/linux/list_nulls.h
+++ b/include/linux/list_nulls.h
@@ -80,10 +80,10 @@ static inline void hlist_nulls_add_head(struct hlist_nulls_node *n,
struct hlist_nulls_node *first = h->first;

n->next = first;
- WRITE_ONCE(n->pprev, &h->first);
+ n->pprev = &h->first;
h->first = n;
if (!is_a_nulls(first))
- WRITE_ONCE(first->pprev, &n->next);
+ first->pprev = &n->next;
}

static inline void __hlist_nulls_del(struct hlist_nulls_node *n)
@@ -99,7 +99,7 @@ static inline void __hlist_nulls_del(struct hlist_nulls_node *n)
static inline void hlist_nulls_del(struct hlist_nulls_node *n)
{
__hlist_nulls_del(n);
- WRITE_ONCE(n->pprev, LIST_POISON2);
+ n->pprev = LIST_POISON2;
}

/**
--
2.20.1
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