Hello. This was reported several times, I believe the first report is http://marc.info/?l=linux-kernel&m=127688978121665. Hmm, 3 years ago. The lockless while_each_thread() is racy and broken, almost every user can loop forever.
Recently people started to report they actually hit this problem in oom_kill.c. This doesn't really matter and I can be wrong, but in fact I do not think they really hit this race, it is very unlikely. Another problem with while_each_thread() is that it is very easy to use it wrongly, and oom_kill.c is the good example. I came to conclusion that it is practically impossible to send a single series which fixes all problems, too many different users. So 1/2 adds the new for_each_thread() interface, and 2/2 fixes oom kill as an example. We obviously need a lot more changes like 2/2 before we can kill while_each_thread() and task_struct->thread_group, but I hope they will be straighforward. And in fact I hope that task->thread_group can go away before we change all users of while_each_thread(). David, et al, I din't actually test 2/2, I do not know how. Please review, although it looks simple. Oleg. include/linux/init_task.h | 2 ++ include/linux/sched.h | 12 ++++++++++++ kernel/exit.c | 1 + kernel/fork.c | 7 +++++++ mm/oom_kill.c | 37 ++++++++++++++++++++----------------- 5 files changed, 42 insertions(+), 17 deletions(-) -- 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/
