> Tracee, finish_callback() path: > > if (action == UTRACE_DETACH) > engine->ops = utrace_detached_ops; > > utrace->reporting = NULL; > > no barries, no utrace->lock() in between. > > Tracer, utrace_barrier() under utrace->lock: > > if (engine->ops == utrace_detached_ops) > return -EXXX; > > if (utrace->reporting != engine) > return 0; > > Afaics, this is racy and should be fixed in utrace level.
Let me see if I'm following you. The scenario you mean is that utrace_barrier() returns zero when there had been a callback in progress but it returned UTRACE_DETACH, and so now the engine is detached. The only guarantee utrace_barrier() claims is ordering with respect to the effects of prior utrace_* calls, and a callback not being in progress right now. This scenario meets that interface contract as stated. It's as if utrace_barrier() had returned zero before that callback ran. But you can tell by external means that your callback has started before you called utrace_barrier(), so you want it to return -ESRCH instead of 0. Is that right? Which external means? Thanks, Roland
