writeLockTimeout is set in SolrIndexWriter.init() method as follows:
if (config.writeLockTimeout != -1) setWriteLockTimeout(config.writeLockTimeout);
but this doesn't have effect because setWriteLockTimeout() is an instance method of IndexWriter and at this moment,
IndexWriter's constructor had already been executed and write.lock had beed obtained in the constructor.
To have effect, we should use IndexWriter.setDefaultWriteLockTimeout() class method before creating SolrIndexWriter instance.
With the attached patch, I moved setWriteLockTimeout() to SolrCore and change it to IndexWriter.setDefaultWriteLockTimeout().
I'm not sure it is an appropriate place, but it works.