Messages in this thread | | | Date | Mon, 2 Dec 2013 16:24:23 +0100 | From | Oleg Nesterov <> | Subject | [PATCH 0/2] initial while_each_thread() fixes |
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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(-)
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