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@xxxxxxxxxx/ 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? Thanks, Oleg.
