On Wed, Feb 21, 2018 at 03:13:10PM -0800, Yang Shi wrote: > >>> 2) access_remote_vm() et al will do the same ->mmap_sem, and > >> Yes, it does. But, __access_remote_vm() is called by access_process_vm() > >> too, which is used by much more places, i.e. ptrace, so I was not sure > >> if it is preferred to convert to killable version. So, I leave it > >> untouched. > > Yeah, but ->mmap_sem is taken 3 times per /proc/*/cmdline read > > and your scalability tests should trigger next backtrace right away. > > Yes, however, I didn't run into it if mmap_sem is acquired earlier. > > How about defining a killable version, like > __access_remote_vm_killable() which use down_read_killable(), then the > killable version can be used by proc/*/cmdline? There might be other > users in the future.
It would be a disaster as interfaces multiply.