[PATCH][gdbsupport] Avoid main thread in parallel for with thread sanitizer

[Tom Tromey]

>>>>> "Tom" == Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> writes:

Tom> When running tasks in a parallel for, some elements may be handled by a worker
Tom> thread and others by the main thread.

Tom> When running with -fsanitize=thread, avoid the main thread in the parallel
Tom> for, to prevent multi-threading problems being hidden.

Tom> Tested on x86_64-linux, with -fsanitize=thread.

Tom> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29359

Tom> Any comments?

I tend to think that different behavior based on the use of a sanitizer
should be avoided.  Otherwise, the sanitizer is not checking what is
actually run.

Tom