On 03/17, Andrew Morton wrote: > > On Fri, 14 Mar 2014 16:46:26 -0400 Joseph Salisbury > <[email protected]> wrote: > > > Hi Tetsuo, > > > > A kernel bug report was opened against Ubuntu[0]. We performed a kernel > > bisect, and found that reverting the following commit resolved this bug: > > > > > > commit 786235eeba0e1e85e5cbbb9f97d1087ad03dfa21 > > Author: Tetsuo Handa <[email protected]> > > Date: Tue Nov 12 15:06:45 2013 -0800 > > > > kthread: make kthread_create() killable > > > > The regression was introduced as of v3.13-rc1. > > > > The bug indicates an issue with the SAS controller during > > initialization, which prevents the system from booting. Additional > > details are available in the bug report or on request. > > > > I was hoping to get your feedback, since you are the patch author. Do > > you think gathering any additional data will help diagnose this issue, > > or would it be best to submit a revert request? > > > > [0] http://pad.lv/1276705 > > What process is running here? Presumably modprobe. > > A possible explanation is that modprobe has genuinely received a > SIGKILL. Can you identify anything in this setup which might send a > SIGKILL to the modprobe process?
See also other discussion in this thread, I thinks the code in drivers/ is buggy anyway. > kthread_create_on_node() thinks that SIGKILL came from the oom-killer > and it cheerfully returns -ENOMEM, which is incorrect if that signal > came from userspace. Yes, I think it should return -EINTR. > And I don't _think_ we prevent > userspace-originated signals from unblocking > wait_for_completion_killable()? And we should not. > Root cause time: it's wrong for the oom-killer to use SIGKILL. Not sure... what else? > In fact > it's basically always wrong to send signals from in-kernel. Well, SIGSEGV, SIGIO... > Signals > are a userspace IPC mechanism and using them in-kernel a) makes it hard > (or impossible) to distinguish them from userspace-originated signals > and b) permits userspace to produce surprising results in the kernel, > which I suspect is what we're seeing here. Well, I think in this case it doesn't matter who/why sends a signal. The task is killed, it should react and exit asap. And kthread_create() can fail in any case, at least the kernel should not crash. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
