On Thu, Aug 18, 2011 at 23:23, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Thu, Aug 18, 2011 at 11:11 AM, Kay Sievers <kay.sievers@xxxxxxxx> wrote: >> >> How about this? It: >> - uses task->real_parent to walk up the chain of parents. > > If I read this right, it does that for all the normal cases too. > Disgusting. Slowing down the *usual* UNIX case for your new made-up > case that nobody actually uses is not acceptable. Re-parenting is not a *usual* operation, usual exit()s have a parent and do not trigger that code. And in most cases of double-forking it is a one step, which is almost the same than it was before. Only if we skip multiple parents it will get the check, which is cheap anyway. > So NAK. We're not slowing down normal code for some new feature that > realistically will never be used by any normal applications. It will be used for all new service managers. UNIX is a pain if you want to watch your children regarding double-forking, if you are not init. And it will clean up the mess the desktop stuff is putting in 'ps afx'. Here is the before/after output: 253 ? Ss 0:00 /bin/dbus-daemon --system --address=systemd: --nofork --systemd-activation 294 ? Sl 0:00 /usr/libexec/polkit-1/polkitd 328 ? S 0:00 /usr/sbin/modem-manager 608 ? Sl 0:00 /usr/libexec/colord 658 ? Sl 0:00 /usr/libexec/upowerd 819 ? Sl 0:00 /usr/libexec/imsettings-daemon 916 ? Sl 0:00 /usr/libexec/udisks-daemon 917 ? S 0:00 \_ udisks-daemon: not polling any devices 294 ? Ss 0:00 /bin/dbus-daemon --system --address=systemd: --nofork --systemd-activation 426 ? Sl 0:00 \_ /usr/libexec/polkit-1/polkitd 449 ? S 0:00 \_ /usr/sbin/modem-manager 635 ? Sl 0:00 \_ /usr/libexec/colord 705 ? Sl 0:00 \_ /usr/libexec/upowerd 959 ? Sl 0:00 \_ /usr/libexec/udisks-daemon 960 ? S 0:00 | \_ udisks-daemon: not polling any devices 977 ? Sl 0:00 \_ /usr/libexec/packagekitd It's a pretty nice way for an admin too see what's going on on that box, even with good old 'ps'. It will also dramatically simplify the handling of started services from a service manager which double-fork for only historic reasons and make proper service supervision a nightmare if you are not PID 1. Upstart ptraces all started services to accomplish something similar. I doubt we want to go that road, but if you prefer ... :) If you want, we can make the forked processes inherit a flag if the 'subreaper' should be looked up at all. Then we have almost zero overhead if the feature isn't used. You think that's needed? Thanks, Kay -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
