From: Lai Jiangshan <laijs@linux.alibaba.com>
To: linux-kernel@vger.kernel.org
Cc: Lai Jiangshan <laijs@linux.alibaba.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
Michel Lespinasse <walken@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Rik van Riel <riel@redhat.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH V2 2/2] rbtree_latch: don't need to check seq when it found a node
Date: Fri, 15 May 2020 15:59:09 +0000 [thread overview]
Message-ID: <20200515155912.1713-2-laijs@linux.alibaba.com> (raw)
In-Reply-To: <20200515155912.1713-1-laijs@linux.alibaba.com>
latch_tree_find() should be protected by caller via RCU or so.
When it find a node in an attempt, the node must be a valid one
in RCU's point's of view even the tree is (being) updated with a
new node with the same key which is entirely subject to timing
anyway.
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
include/linux/rbtree_latch.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/rbtree_latch.h b/include/linux/rbtree_latch.h
index 638942f53c0a..affc4b026d9b 100644
--- a/include/linux/rbtree_latch.h
+++ b/include/linux/rbtree_latch.h
@@ -245,7 +245,7 @@ latch_tree_find(void *key, struct latch_tree_root *root,
do {
seq = raw_read_seqcount_latch(&root->seq);
node = __lt_find(key, root, seq & 1, ops->comp);
- } while (read_seqcount_retry(&root->seq, seq));
+ } while (!node && read_seqcount_retry(&root->seq, seq));
return node;
}
--
2.20.1
next prev parent reply other threads:[~2020-05-15 15:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-15 12:47 [PATCH 1/2] rbtree_latch: quit searching when reaching to maximum depth Lai Jiangshan
2020-05-15 12:47 ` [PATCH 2/2] rbtree_latch: don't need to check seq when it found a node Lai Jiangshan
2020-05-15 13:04 ` Peter Zijlstra
2020-05-15 13:00 ` [PATCH 1/2] rbtree_latch: quit searching when reaching to maximum depth Peter Zijlstra
2020-05-15 14:39 ` Lai Jiangshan
2020-05-15 15:01 ` Peter Zijlstra
2020-05-15 15:59 ` [PATCH V2 " Lai Jiangshan
2020-05-15 15:59 ` Lai Jiangshan [this message]
2020-05-16 4:27 ` [PATCH V2 2/2] rbtree_latch: don't need to check seq when it found a node Michel Lespinasse
2020-05-16 4:52 ` Lai Jiangshan
2020-05-16 5:03 ` Michel Lespinasse
2020-05-23 0:56 ` [PATCH V2 1/2] rbtree_latch: quit searching when reaching to maximum depth Lai Jiangshan
2020-05-15 13:14 ` [PATCH " Mathieu Desnoyers
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