Messages in this thread | | | Date | Thu, 16 Nov 2023 06:52:16 -0500 | Subject | Re: [PATCH 0/3] bpf: kernel/bpf/task_iter.c: don't abuse next_thread() | From | Yonghong Song <> |
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On 11/16/23 4:54 AM, Oleg Nesterov wrote: > On 11/15, Yonghong Song wrote: >> On 11/14/23 11:32 AM, Oleg Nesterov wrote: >>> Compile tested. >>> >>> Every lockless usage of next_thread() was wrong, bpf/task_iter.c is >>> the last user and is no exception. >> It would be great if you can give more information in the commit message >> about why the usage of next_thread() is wrong in bpf/task_iter.c. > I tried to explain the problems in the changelogs: > > 1/3: > task_group_seq_get_next() can return the group leader twice if it races > with mt-thread exec which changes the group->leader's pid. > > 2/3: > bpf_iter_task_next() can loop forever, "kit->pos == kit->task" can never > happen if kit->pos execs. > >> IIUC, some information is presented in : >> https://lore.kernel.org/all/20230824143112.GA31208@redhat.com/ > Yes, Linus and Eric suggest to simply kill next_thread(). I am not > sure, this needs another discussion. > > But as for bpf/task_iter.c... Even _if_ the usage was correct, this > code simply doesn't need the "circular" next_thread(), NULL at the > end simplifies the code. > >> Also, please add 'bpf' in the subject tag ([PATCH bpf 0/3]) to >> make it clear the patch should be applied to bpf tree. > OK, will do next time. Or should I resend this series with 'bpf' > in the subject tag?
There is no need then. We can wait for maintainers who may or may not have additional requests.
> > Thanks, > > Oleg. >
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