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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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