From 429e7141f2f41c1d66dd4dd711a47ca9e0f0c2cb Mon Sep 17 00:00:00 2001
From: Nishant Das <nishdas93@gmail.com>
Date: Thu, 26 Nov 2020 05:16:36 +0800
Subject: [PATCH] p2p/discover: fix deadlock in discv5 message dispatch
(#21858)
This fixes a deadlock that could occur when a response packet arrived
after a call had already received enough responses and was about to
signal completion to the dispatch loop.
Co-authored-by: Felix Lange <fjl@twurst.com>
---
p2p/discover/v5_udp.go | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/p2p/discover/v5_udp.go b/p2p/discover/v5_udp.go
index c95317a00..9dd2b3173 100644
--- a/p2p/discover/v5_udp.go
+++ b/p2p/discover/v5_udp.go
@@ -454,9 +454,20 @@ func (t *UDPv5) call(node *enode.Node, responseType byte, packet v5wire.Packet)
// callDone tells dispatch that the active call is done.
func (t *UDPv5) callDone(c *callV5) {
- select {
- case t.callDoneCh <- c:
- case <-t.closeCtx.Done():
+ // This needs a loop because further responses may be incoming until the
+ // send to callDoneCh has completed. Such responses need to be discarded
+ // in order to avoid blocking the dispatch loop.
+ for {
+ select {
+ case <-c.ch:
+ // late response, discard.
+ case <-c.err:
+ // late error, discard.
+ case t.callDoneCh <- c:
+ return
+ case <-t.closeCtx.Done():
+ return
+ }
}
}
--
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