Messages in this thread Patch in this message | | | Date | Fri, 8 Nov 2019 11:24:48 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 1/2] list: add hlist_unhashed_lockless() |
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On Thu, Nov 07, 2019 at 11:37:37AM -0800, Eric Dumazet wrote: > We would like to use hlist_unhashed() from timer_pending(), > which runs without protection of a lock. > > Note that other callers might also want to use this variant. > > Instead of forcing a READ_ONCE() for all hlist_unhashed() > callers, add a new helper with an explicit _lockless suffix > in the name to better document what is going on. > > Also add various WRITE_ONCE() in __hlist_del(), hlist_add_head() > and hlist_add_before()/hlist_add_behind() to pair with > the READ_ONCE(). > > Signed-off-by: Eric Dumazet <edumazet@google.com> > Cc: "Paul E. McKenney" <paulmck@kernel.org> > Cc: Thomas Gleixner <tglx@linutronix.de>
I have queued this, but if you prefer it go some other way:
Acked-by: Paul E. McKenney <paulmck@kernel.org>
But shouldn't the uses in include/linux/rculist.h also be converted into the patch below? If so, I will squash the following into your patch.
Thanx, Paul
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diff --git a/include/linux/rculist.h b/include/linux/rculist.h index 61c6728a..4b7ae1b 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -173,7 +173,7 @@ static inline void hlist_del_init_rcu(struct hlist_node *n) { if (!hlist_unhashed(n)) { __hlist_del(n); - n->pprev = NULL; + WRITE_ONCE(n->pprev, NULL); } } @@ -473,7 +473,7 @@ static inline void list_splice_tail_init_rcu(struct list_head *list, static inline void hlist_del_rcu(struct hlist_node *n) { __hlist_del(n); - n->pprev = LIST_POISON2; + WRITE_ONCE(n->pprev, LIST_POISON2); } /** @@ -489,11 +489,11 @@ static inline void hlist_replace_rcu(struct hlist_node *old, struct hlist_node *next = old->next; new->next = next; - new->pprev = old->pprev; + WRITE_ONCE(new->pprev, old->pprev); rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new); if (next) - new->next->pprev = &new->next; - old->pprev = LIST_POISON2; + WRITE_ONCE(new->next->pprev, &new->next); + WRITE_ONCE(old->pprev, LIST_POISON2); } /* @@ -528,10 +528,10 @@ static inline void hlist_add_head_rcu(struct hlist_node *n, struct hlist_node *first = h->first; n->next = first; - n->pprev = &h->first; + WRITE_ONCE(n->pprev, &h->first); rcu_assign_pointer(hlist_first_rcu(h), n); if (first) - first->pprev = &n->next; + WRITE_ONCE(first->pprev, &n->next); } /** @@ -564,7 +564,7 @@ static inline void hlist_add_tail_rcu(struct hlist_node *n, if (last) { n->next = last->next; - n->pprev = &last->next; + WRITE_ONCE(n->pprev, &last->next); rcu_assign_pointer(hlist_next_rcu(last), n); } else { hlist_add_head_rcu(n, h); @@ -592,10 +592,10 @@ static inline void hlist_add_tail_rcu(struct hlist_node *n, static inline void hlist_add_before_rcu(struct hlist_node *n, struct hlist_node *next) { - n->pprev = next->pprev; + WRITE_ONCE(n->pprev, next->pprev); n->next = next; rcu_assign_pointer(hlist_pprev_rcu(n), n); - next->pprev = &n->next; + WRITE_ONCE(next->pprev, &n->next); } /** @@ -620,10 +620,10 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n, struct hlist_node *prev) { n->next = prev->next; - n->pprev = &prev->next; + WRITE_ONCE(n->pprev, &prev->next); rcu_assign_pointer(hlist_next_rcu(prev), n); if (n->next) - n->next->pprev = &n->next; + WRITE_ONCE(n->next->pprev, &n->next); } #define __hlist_for_each_rcu(pos, head) \
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