On Wed 16-03-22 19:49:38, Charan Teja Kalla wrote: [...] > It can return EINTR when: > ------------------------- > 1) PTRACE_MODE_READ is being checked in mm_access() where it is waiting > on task->signal->exec_update_lock. EINTR returned from here guarantees > that process_madvise() didn't event start processing. > https://elixir.bootlin.com/linux/v5.16.14/source/mm/madvise.c#L1264 --> > https://elixir.bootlin.com/linux/v5.16.14/source/kernel/fork.c#L1318 > > 2) The process_madvise() started processing VMA's but the required > behavior on a VMA needs mmap_write_lock_killable(), from where EINTR is > returned. Please note this will happen if the task has been killed. The return value doesn't really matter because the process won't run in userspace. > The current behaviours supported by process_madvise(), > MADV_COLD, PAGEOUT, WILLNEED, just need read lock here. > https://elixir.bootlin.com/linux/v5.16.14/source/mm/madvise.c#L1164 > **Thus I think no way for EINTR can be returned by process_madvise() in > the middle of processing.** . No? Maybe not with the current implementation but I can easily imagine that there is a requirement to break out early when there is a signal pending (e.g. to support terminating madvise on a large memory rage). You would get EINTR then somehow need to communicate that to the userspace. -- Michal Hocko SUSE Labs
