Re: [PATCH] Make udev reload rules quiet during bootup

[Dave Young]

Hi Kairui,
On 11/22/18 at 11:05pm, Kairui Song wrote:
> In commit 1c97aee and commit 227c185 udev rules was rewritten to use
> systemd-run to run in a non-blocking mode. The problem is that it's a
> bit noise, especially on machine bootup, systemd will always generate
> extra logs for service start, you might see your journal full of lines
> like these if you have many CPUs (each CPU generates a udev event on
> boot):
>
> ...
> Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
> Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
> Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
> Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
> ...
>
> While system is still booting up, kdump service is not started yet, so
> systemd-run calls will end up doing nothing, the throttler being called
> by systemd-run will just exit if kdump is not loaded.
>
> This patch avoid systemd-run from being called at first place if kdump
> service is not running, so there won't be unnecessary logs.
>
> As udev rules don't support shell expressions, this patch reuse
> the kdump-udev-throttler script, adding a --no-block option.
> kdump-udev-throttler will call it self with systemd-run to run in non
> blocking mode if --no-block is given, and exit before doing anything if
> kdump is not started. Udev just call "kdump-udev-throttler --no-block"
> directly.
> Signed-off-by: Kairui Song
>
> 98-kexec.rules       |  2 +-
>  kdump-udev-throttler | 13 ++++++++++---
>  2 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/98-kexec.rules b/98-kexec.rules
> index 2f88c77..eca909e 100644
> --- a/98-kexec.rules
> +++ b/98-kexec.rules
> @@ -7,6 +7,6 @@ GOTO="kdump_reload_end"
>
> LABEL="kdump_reload"
>
> -RUN+="/usr/bin/systemd-run --no-block /usr/lib/udev/kdump-udev-throttler"
> +RUN+="/usr/lib/udev/kdump-udev-throttler --no-block"

This fix looks a hack, if it doable to conditionally run "/usr/lib/udev/kdump-udev-throttler --no-block"
in udev rule?
> LABEL="kdump_reload_end"
> diff --git a/kdump-udev-throttler b/kdump-udev-throttler
> index 6cbb99a..6899379 100755
> --- a/kdump-udev-throttler
> +++ b/kdump-udev-throttler
> @@ -13,13 +13,20 @@
>  # In this way, we can make sure kdump service is restarted immediately
>  # and for exactly once after udev events are settled.
>
> throttle_lock="/var/lock/kdump-udev-throttle"
> -interval=2
>
> -# Don't reload kdump service if kdump service is not started by systemd
> +# Don't do anything if kdump service is not started by systemd
>  systemctl is-active kdump.service &>/dev/null || exit 0
>
> +if [[ $1 == '--no-block' ]]; then
>    systemd-run --no-block --quiet $0
>    if [[ $? -ne 0 ]]; then
>            echo "kdump-udev-throttler: Failed to call systemd-run"
>            exit 1
>    fi
>    exit 0
>
> +fi
>
> exec 9>$throttle_lock
>  if [ $? -ne 0 ]; then
>          echo "Failed to create the lock file! Fallback to non-throttled kdump service restart"
> -- 
> 2.19.1

Thanks
Dave