[Buildroot] [PATCH] package/skeleton: add a startup script to wait for slow network interfaces

[Arnout Vandecappelle <arnout@mind.be>]

On 03-10-15 19:29, Maxime Hadjinlian wrote:
> 
> 
> On Sat, Oct 3, 2015 at 5:47 PM, Thomas Petazzoni
> <thomas.petazzoni@free-electrons.com
> <mailto:thomas.petazzoni@free-electrons.com>> wrote:
> 
>     Hello,
> 
>     On Sat,  3 Oct 2015 14:31:45 +0100, Yann E. MORIN wrote:
> 
>     > +    printf "Waiting for interface %s to appear" "${IF}"
>     > +    wait=${WAIT_DELAY}
>     > +    while [ ${wait} -gt 0 ]; do
>     > +        if [ -e "/sys/class/net/${IF}" ]; then
>     > +            printf " yes\n"
>     > +            return 0
>     > +        fi
>     > +        sleep 1
>     > +        printf "."
>     > +        : $((wait--))
>     > +    done
> 
>     One thing that I really like in Buildroot is that by default, it
>     generates you a system that boots really fast. People often don't have
>     to do anything special with Buildroot to make it boot fast. So having a
>     shell script that is installed by default and does a "sleep 1" in a
>     loop is not very nice :-/
> 
>     Though I agree that it will only slow the boot on systems where the
>     network interfaces are not available immediately at boot time.
> 
> I have that trouble too but instead of doing a sleep 1, I "hammer" the system
> with sleep 0.1 or usleep 25 if it's available (even usleep 1 can work, since
> it's not RT, it takes around 10ms).

 Since sysv init is not parallel, you're not even hammering the system since
nothing else is going on except perhaps some hotplug callbacks.

 Regards,
 Arnout

> This way it's almost transparent and add the necessary requirements before going
> on with the boot.
> 
> 
>     Thomas
>     --
>     Thomas Petazzoni, CTO, Free Electrons
>     Embedded Linux, Kernel and Android engineering
>     http://free-electrons.com
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> 
> 
> 
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-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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