decoder/{dsdiff,dsf,opus}: fix deadlock while seeking

NEWS

 ver 0.19.5 (not yet released)
+* decoder
+  - dsdiff, dsf, opus: fix deadlock while seeking
 
 ver 0.19.4 (2014/11/18)
 * protocol

src/decoder/plugins/DsdLib.cxx

@@ -53,7 +53,7 @@ dsdlib_skip_to(Decoder *decoder, InputStream &is,
 	       offset_type offset)
 {
 	if (is.IsSeekable())
-		return is.Seek(offset, IgnoreError());
+		return is.LockSeek(offset, IgnoreError());
 
 	if (is.GetOffset() > offset)
 		return false;
@@ -72,7 +72,7 @@ dsdlib_skip(Decoder *decoder, InputStream &is,
 		return true;
 
 	if (is.IsSeekable())
-		return is.Seek(is.GetOffset() + delta, IgnoreError());
+		return is.LockSeek(is.GetOffset() + delta, IgnoreError());
 
 	if (delta > 1024 * 1024)
 		/* don't skip more than one megabyte; it would be too

src/decoder/plugins/OpusDecoderPlugin.cxx

@@ -214,7 +214,7 @@ LoadEOSPacket(InputStream &is, Decoder *decoder, int serialno,
 	ogg_stream_clear(&os);
 
 	/* restore the previous file position */
-	is.Seek(old_offset, IgnoreError());
+	is.LockSeek(old_offset, IgnoreError());
 
 	return result;
 }