On Mon, Mar 18, 2013 at 06:03:02PM +0100, Oleg Nesterov wrote: > > Assume that's not happening, why would ptrace give me -ESRCH, yet > > /proc/<pid>/status would show me ptrace attached to the thread. > > And why do you think this should be explained by SIGKILL?
It's an assumption, if I knew before you would be getting a patch instead of an email. > > > Please explain what difference this patch makes in your testing. > > > > I haven't tested with or with out it, I've just read the code and it > > seems to be the only way I'm getting ESRCH back from ptrace.. > > No, > > > For instance, I ptrace attach from inside the corepipe_app then try > > PTRACE_GETREGS and you get -ESRCH . > > Sure. PTRACE_GETREGS and (almost) any other request can only succeed > if the tracee is TASK_TRACED! I already told you that ptrace() doesn't > and can't work exactly because the dumper never does ptrace_stop(). When does ptrace_stop run ? > > > > It can give me it's registers, and allow me access to it's memory space. > > > > That's all I want realistically .. > > > > > > ... > > > > > > > I'm trying to get the "dumpers" registers and stack out when it fails. > > > > > > Can't you read the generated core for that? And see below... > > > > I'm not sure if it would accomplish what I need. I can't save the whole > > core, > > and I can't get memory to save large chunks of it. > > Not sure I understand this part... The above is regarding the situation which I'm running my corepipe_app , i.e. my system doesn't have a disk to save a core file for parsing. > > > > Oh, I think I see what you mean. I would ptrace attach prior to the > > thread crashing , > > I don't understand what "prior to the thread crashing" means... the pipe > hanlder is spawned after the task has already initiated the coredump... > IOW, other threads are already killed and we are ready to actually dump > the core. I can't attach to the thread after it's crashed, since I get ESRCH in the corepipe_app for every operation, so that suggests I'd need to attach prior to when it crashes. > > and get an event for when it crashes ? > > And get an event after coredump_app closes the pipe. Assuming that > you use PTRACE_SEIZE(PTRACE_O_CORE_DUMPED) rather that PTRACE_ATTACH. > And assuming you do this before you close the pipe, otherwise it can > exit before you do PTRACE_SEIZE. So corepipe_app would PTRACE_SEIZE then close the pipe but continue running ? > > > Of course, this can't help to ptrace/inspect other threads, they are > > > already (well, almost) dead at this point. > > > > Ideally I would want to attach after it crashes, cause other wise I'd > > have to ptrace attach to a lot of threads (to monitor the whole system). > > See above. You do not need to attach in advance. > > But once again, you can't attach the sub-threads, they are already dead > when coredump_app is called. PTRACE_ATTACH will work but this can help, > a sub-thread will never report any event and PF_EXITING is already set. Ok .. Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
