From 8d815e365cd2cda2e865dd2e272ebb5a3d4b8772 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Thu, 20 Jun 2019 08:36:27 +0200
Subject: [PATCH] rpc: fix rare deadlock when canceling HTTP call context
(#19715)
When cancelling the context for a call on a HTTP-based client while the
call is running, the select in requestOp.wait may hit the <-context.Done()
case instead of the <-op.resp case. This doesn't happen often -- our
cancel test hasn't caught this even though it ran thousands of times
on CI since the RPC client was added.
Fixes #19714
---
rpc/client.go | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/rpc/client.go b/rpc/client.go
index 02029dc8f..16511747f 100644
--- a/rpc/client.go
+++ b/rpc/client.go
@@ -137,9 +137,11 @@ func (op *requestOp) wait(ctx context.Context, c *Client) (*jsonrpcMessage, erro
select {
case <-ctx.Done():
// Send the timeout to dispatch so it can remove the request IDs.
- select {
- case c.reqTimeout <- op:
- case <-c.closing:
+ if !c.isHTTP {
+ select {
+ case c.reqTimeout <- op:
+ case <-c.closing:
+ }
}
return nil, ctx.Err()
case resp := <-op.resp: