On Tue, Mar 26, 2019 at 9:23 AM Christian Brauner <christian@xxxxxxxxxx> wrote: > > On Tue, Mar 26, 2019 at 09:17:07AM -0700, Daniel Colascione wrote: > > Thanks for the patch. > > > > On Tue, Mar 26, 2019 at 8:55 AM Christian Brauner <christian@xxxxxxxxxx> wrote: > > > > > > The pidctl() syscalls builds on, extends, and improves translate_pid() [4]. > > > I quote Konstantins original patchset first that has already been acked and > > > picked up by Eric before and whose functionality is preserved in this > > > syscall: > > > > We still haven't had a much-needed conversation about splitting this > > system call into smaller logical operations. It's important that we > > address this point before this patch is merged and becomes permanent > > kernel ABI. > > I don't particularly mind splitting this into an additional syscall like > e.g. pidfd_open() but then we have - and yes, I know you'll say > syscalls are cheap - translate_pid(), and pidfd_open(). What I like > about this rn is that it connects both apis in a single syscall > and allows pidfd retrieval across pid namespaces. So I guess we'll see > what other people think. Thanks. I also appreciate a clean unification of related functionality, but I'm concerned that this API in particular --- due in part to its *ctl() name --- will become a catch-all facility for doing *anything* with processes. (Granted, heavy use of a new, good, and clean API would be a good problem to have.) This single-system-call state of affairs would make it more awkward than necessary to do system-call level logging (say, strace -e), enable or disable tracing of specific operations with ftrace, apply some kinds of SELinux policy, and so on, and the only advantage of the single system call design that I can see right now is the logical cleanliness. I'd propose splitting the call, or if we can't do that, renaming it to something else --- pidfd_query --- so that it's less likely to become a catch-all operation holder.
