ASSERT signal.c:3806 info->interrupted == NULL || info->interrupted == f

Running an app that links DR statically and does an internal attach hits this assert maybe 1 in 10,000 runs, after attach is finished.

<Attached to 97 threads in application >
<Application .  Internal Error: DynamoRIO debug check failure: core/unix/signal.c:3806 info->interrupted == NULL || info->interrupted == f
(Error occurred @11002 frags)
internal version, custom build