On Sat, Jun 18, 2022 at 12:41:11PM +0100, Ralph Corderoy wrote: > Hi Nate, > > > One manifestation of this is a race conditions in system(), which > > (depending on the implementation) is non-atomic in that it first calls > > a fork() and then an exec(). > > The need for O_CLOFORK might be made more clear by looking at a > long-standing Go issue, i.e. unrelated to system(3), which was started > in 2017 by Russ Cox when he summed up the current race-condition > behaviour of trying to execve(2) a newly created file: > https://github.com/golang/go/issues/22315. I raised it on linux-kernel > in 2017, https://marc.info/?l=linux-kernel&m=150834137201488, and linked > to a proposed patch from 2011, ‘[PATCH] fs: add FD_CLOFORK and > O_CLOFORK’ by Changli Gao. As I said, long-standing. The problem is that people advocating for O_CLOFORK understand its value, but not its cost. Other google employees have a system which has literally millions of file descriptors in a single process. Having to maintain this extra state per-fd is a cost they don't want to pay (and have been quite vocal about earlier in this thread). Fundamentally, fork()+exec() is a terrible model. Mind you, so is spawn(). I haven't seen a good model yet.
