[arch-dev-public] Hooks!

[Dave Reisner]

On Mon, May 02, 2016 at 05:10:15PM +0200, Christian Hesse wrote:
> Gerardo Exequiel Pozzi <vmlinuz386 at gmail.com> on Mon, 2016/05/02 08:46:
> > On 05/02/16 07:20, Christian Hesse wrote:
> > > Massimiliano Torromeo <massimiliano.torromeo at gmail.com> on Fri, 2016/04/29
> > > 12:47:  
> > >> I was also wondering about a pacman hook ro run "systemctl daemon-reload"
> > >> after systemd units installations/upgrades. This is something that was
> > >> not done even in .install files but I don't know if there was a reason
> > >> why.
> > >>
> > >> Others distros do this automatically, even the ones that do not have the
> > >> bad habit of restarting the services for you without asking. Eg: I never
> > >> had to do daemon-reload on CentOS 7.
> > >>
> > >> As far as I understand it shouldn't have any unintended side effects
> > >> (and I certainly never experienced one). Thoughts?  
> > > 
> > > Ah, and another one to reload udev rules:
> > > 
> > > [Trigger]
> > > Operation = Install
> > > Operation = Upgrade
> > > Operation = Remove
> > > Type = File
> > > Target = usr/lib/udev/rules.d/*
> > > 
> > > [Action]
> > > Description = Reload udev rule files
> > > When = PostTransaction
> > > Exec = /usr/bin/udevadm control --reload-rules
> > > Depends = systemd
> > >   
> > 
> > --reload-rules (is keep but hidden for compatibility), renamed to
> > --reload,
> 
> Ah, did not notice, yet.
> 
> > in any case, rules are reloaded automagically (thanks to inotify).
> 
> Are you sure? Even attached strace to systemd-udevd and could not see any
> activity when changing files in /usr/lib/udev/rules.d/.

inotify hasn't been used in years. This is the current mechanism:

https://github.com/systemd/systemd/blob/master/src/udev/udevd.c#L796

Rules won't be reloaded until there are events to process, and it's
rate-limited to a max of once every 3 seconds.