[PATCH] utrace: utrace_reset() should clear TIF_SINGLESTEP if no more engines

[Roland McGrath]

> Change utrace_reset() to do user_disable_single_step(). Alternatively
> we could change ptrace layer, but I think this is not ptrace specific.

Yes, it's right to fix this in the utrace layer.  
But I'm not sure that's the right place in the code to fix it.

The expectation is that either we'll get to finish_resume_report,
which calls user_*_step, or that utrace_control is resuming us
without any expectation of a report.  For UTRACE_RESUME in that
case, utrace_control calls user_disable_single_step.  So probably
the UTRACE_DETACH case there should just do it to.


Thanks,
Roland