From: Matt Joiner <anacrolix@gmail.com>
Date: Fri, 29 Dec 2017 01:15:33 +0000 (+1100)
Subject: Survive panics while writing chunks
X-Git-Tag: v1.0.0~310
X-Git-Url: http://www.git.stargrave.org/?a=commitdiff_plain;h=f408e19a7a712913b05731300389383e5cc9a9f2;p=btrtrc.git

Survive panics while writing chunks

Also improve the comment on that code
---

diff --git a/connection.go b/connection.go
index b8756215..7d94f08b 100644
--- a/connection.go
+++ b/connection.go
@@ -1061,11 +1061,17 @@ func (c *connection) receiveChunk(msg *pp.Message) {
 		c.postCancel(req)
 	}
 
-	cl.mu.Unlock()
-	// Write the chunk out. Note that the upper bound on chunk writing
-	// concurrency will be the number of connections.
-	err := t.writeChunk(int(msg.Index), int64(msg.Begin), msg.Piece)
-	cl.mu.Lock()
+	err := func() error {
+		cl.mu.Unlock()
+		defer cl.mu.Lock()
+		// Write the chunk out. Note that the upper bound on chunk writing
+		// concurrency will be the number of connections. We write inline with
+		// receiving the chunk (with this lock dance), because we want to
+		// handle errors synchronously and I haven't thought of a nice way to
+		// defer any concurrency to the storage and have that notify the
+		// client of errors. TODO: Do that instead.
+		return t.writeChunk(int(msg.Index), int64(msg.Begin), msg.Piece)
+	}()
 
 	piece.decrementPendingWrites()