Re: [PATCH V2 dracut 2/2] watchdog: install module for active watchdog

[Pratyush Anand <panand-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On 04/03/2016:12:56:10 PM, Dave Young wrote:
> Hi, Pratyush
> 
> [snip]
> > diff --git a/modules.d/04watchdog/module-setup.sh b/modules.d/04watchdog/module-setup.sh
> > index 7ec757aec032..6232afb0d9ca 100755
> > --- a/modules.d/04watchdog/module-setup.sh
> > +++ b/modules.d/04watchdog/module-setup.sh
> > @@ -32,3 +32,36 @@ install() {
> >      inst_multiple -o wdctl
> >  }
> >  
> > +installkernel() {
> > +    cd /sys/class/watchdog
> > +    for dir in */; do
> > +	    cd $dir
> > +	    active=`[ -f state ] && cat state`
> > +	    if [ "$active" =  "active" ]; then
> > +		    # applications like kdump need to know that, which
> > +		    # watchdog modules have been added into initramfs
> > +		    echo `cat identity` >> "$initdir/tmp/active-watchdogs"
> > +		    # device/modalias will return driver of this device
> > +		    wdtdrv=`cat device/modalias`
> > +		    # There can be more than one module represented by same
> > +		    # modalias. Currently load all of them.
> > +		    # TODO: Need to find a way to avoid any unwanted module
> > +		    # represented by modalias
> > +		    wdtdrv=`modprobe -R $wdtdrv | tr "\n" "," | sed 's/.$//'`
> > +		    instmods $wdtdrv
> > +		    # however in some cases, we also need to check that if
> > +		    # there is a specific driver for the parent bus/device.
> > +		    # In such cases we also need to enable driver for parent
> > +		    # bus/device.
> > +		    wdtppath="device/..";
> > +		    while [ -f "$wdtppath/modalias" ]
> > +		    do
> > +			    wdtpdrv=`cat $wdtppath/modalias`
> > +			    wdtpdrv=`modprobe -R $wdtpdrv | tr "\n" "," | sed 's/.$//'`
> > +			    instmods $wdtpdrv
> > +			    wdtppath="$wdtppath/.."
> > +		    done
> > +	    fi
> > +	    cd ..
> > +    done
> > +}
> 
> Another thing coming into mind is it possible more than one wdt being active
> at the same time? If so it will cause problem because only the first occupies
> /dev/watchdog device for systemd use?

I had thought about it. Practically I do not see an use case of two active
watchdogs in a system. May be Don can comment better. However, technically it is
possible to have two active watchdog and systemd is using second active watchdog
for system reset. First watchdog might not be connected to reset circuitry and
its interrupt is being used for some other purpose. So, I left it like this.

~Pratyush
> 
> How about just break the loop when we find an active wdt? Is it safe?
> 
> Thanks
> Dave