ASSERT dispatch.c:752 with start/stop attach/detach added to api.detach_spawn

The test in attached patch that basically just extends api.detach_spawn to include some start/stop testing consistently runs into an internal error like this:

Start 288: code_api|api.detach_spawn_stress

[..]

<Application /usr/local/google/home/hgreving/dynamorio/build/suite/tests/bin/api.detach_spawn_stress (137260).  Internal Error: DynamoRIO debug check failure: /usr/local/google/home/hgreving/dynamorio/src/core/dispatch.c:752 wherewasi == DR_WHERE_FCACHE || wherewasi == DR_WHERE_TRAMPOLINE || wherewasi == DR_WHERE_APP                                
288: (Error occurred @795 frags)

Note that not spawning "child" threads eliminates the failure. I don't see anything in the test that shouldn't be supported. The failure should get analyzed.

0001-iX-Reproduce-Internal-Error-api.detach_spawn_stress.patch.zip