> And. If we have multiple tracers, then utrace_control(SINGLESTEP) just > "fools" the caller, another engine can do utrace_control(RESUME) at any > moment.
Sure, but more likely nobody will. > I think you are right, utrace_control() should simply consider UTRACE_XXXSTEP > as UTRACE_REPORT. All else being equal, I still think it would be preferable to optimize when we can. If nobody else used UTRACE_REPORT lately, then they official don't care whether it's stopped, or running, or stepping, or what. If you can just resume it stepping without going through utrace_resume, that is ideal. I'm not sure, but there might be a benefit on some machines to doing user_enable_single_step from the other thread and letting its effects come in with context-switch. (That keeps the arch details of the performance profile the same as with old ptrace.) Thanks, Roland
