Drop support for go 1.20

[btrtrc.git] / reader.go

diff --git a/reader.go b/reader.go
index 34e0f48927b7b466382598897a1537e03bced6d5..4b20206cbf2ecc675ccde147cecc278ebc688040 100644 (file)
--- a/reader.go
+++ b/reader.go
@@ -12,7 +12,7 @@ import (
 )
 
 // Accesses Torrent data via a Client. Reads block until the data is available. Seeks and readahead
-// also drive Client behaviour.
+// also drive Client behaviour. Not safe for concurrent use.
 type Reader interface {
        io.ReadSeekCloser
        missinggo.ReadContexter
@@ -245,24 +245,37 @@ func (r *reader) readOnceAt(ctx context.Context, b []byte, pos int64) (n int, er
                        err = nil
                        return
                }
-               r.t.cl.lock()
-               // TODO: Just reset pieces in the readahead window. This might help
-               // prevent thrashing with small caches and file and piece priorities.
-               r.log(log.Fstr("error reading torrent %s piece %d offset %d, %d bytes: %v",
-                       r.t.infoHash.HexString(), firstPieceIndex, firstPieceOffset, len(b1), err))
-               if !r.t.updatePieceCompletion(firstPieceIndex) {
-                       r.log(log.Fstr("piece %d completion unchanged", firstPieceIndex))
-               }
-               // Update the rest of the piece completions in the readahead window, without alerting to
-               // changes (since only the first piece, the one above, could have generated the read error
-               // we're currently handling).
-               if r.pieces.begin != firstPieceIndex {
-                       panic(fmt.Sprint(r.pieces.begin, firstPieceIndex))
-               }
-               for index := r.pieces.begin + 1; index < r.pieces.end; index++ {
-                       r.t.updatePieceCompletion(index)
+               if r.t.closed.IsSet() {
+                       err = fmt.Errorf("reading from closed torrent: %w", err)
+                       return
                }
-               r.t.cl.unlock()
+               r.t.cl.lock()
+               // I think there's a panic here caused by the Client being closed before obtaining this
+               // lock. TestDropTorrentWithMmapStorageWhileHashing seems to tickle occasionally in CI.
+               func() {
+                       // Just add exceptions already.
+                       defer r.t.cl.unlock()
+                       if r.t.closed.IsSet() {
+                               // Can't update because Torrent's piece order is removed from Client.
+                               return
+                       }
+                       // TODO: Just reset pieces in the readahead window. This might help
+                       // prevent thrashing with small caches and file and piece priorities.
+                       r.log(log.Fstr("error reading torrent %s piece %d offset %d, %d bytes: %v",
+                               r.t.infoHash.HexString(), firstPieceIndex, firstPieceOffset, len(b1), err))
+                       if !r.t.updatePieceCompletion(firstPieceIndex) {
+                               r.log(log.Fstr("piece %d completion unchanged", firstPieceIndex))
+                       }
+                       // Update the rest of the piece completions in the readahead window, without alerting to
+                       // changes (since only the first piece, the one above, could have generated the read error
+                       // we're currently handling).
+                       if r.pieces.begin != firstPieceIndex {
+                               panic(fmt.Sprint(r.pieces.begin, firstPieceIndex))
+                       }
+                       for index := r.pieces.begin + 1; index < r.pieces.end; index++ {
+                               r.t.updatePieceCompletion(index)
+                       }
+               }()
        }
 }