Hi Roman, On 01/28, Roman Gushchin wrote: > > Yes, I think you're right: cgroup_exit() should check CGRP_FREEZE bit, > not CGRP_FROZEN. Like cgroup_post_fork() does (a one-liner change below). but this won't fix all problems? it seems that you missed my other concerns. Firstly, this doesn't look consistent. Suppose a cgroup contains a single process sleeping in ptrace_stop(). Then it becomes CGRP_FROZEN right after "echo 1 > cgroup.freeze". OTOH. if this single task sleeps in do_freezer_trap() and gets PTRACE_INTERRUPT, it will equally sleep ptrace_stop() but cgroup won't be CGRP_FROZEN. Never. Worse, this looks just wrong. In the latter case, cgroup becomes CGRP_FROZEN right after a 2nd task migrates to this cgroup, before this new task calls do_freezer_trap() or cgroup_enter_stopped(). > About spurious transitions (like frozen->non frozen->frozen on a task > being SIGKILLed): > in early versions of the patchset I've tried to avoid them, but then > following the Tejun's advice > switched over to expose them to a user. The logic behind is simple: if > the state of the cgroup has been changed (a task is gone, for > example), let's notify a user. OK, I won't argue... actually I can't argue because I do not really understand why do we want a "killable" freezer, let alone ptraceable ;) Oleg.
