Mdadm monitor sometimes doesn't send events.

["Arkadiusz Bubała" <arkadiusz.bubala@open-e.com>]

Hello,
We've got a problem that sometimes mdadm monitor doesn't send events. 
Actions are as follows:

start:
create new RAID 5 array
wait until it's rebuilding
stop created array
go to start

Only first time we get "NewArray" event then when new array is created 
only "RebuildStarted" event appears. After our analysis we found out 
that when we stop an array we get "DeviceDisapeared" event and when we 
create a new array we get "RebuildFinished" and then "RebuildStarted" 
event. Sometimes those two events don't show up.
The problem is in mdstat_read function:

else if (ent->percent == -1 && w[0] >= '0' && w[0] <= '9' && w[l-1] == 
'%') {
     ent->percent = atoi(w);
}

atoi(w) sometimes returns 0 instead -1. It causes that mse->percent = 0 in:

             if (mse &&
                 mse->percent == -1 &&
                 st->percent >= 0)
                 alert("RebuildFinished", dev, NULL, mailaddr, mailfrom, 
alert_cmd, dosyslog);

and above conditions aren't met. Then in:

             if (mse)
                 st->percent = mse->percent;

st->percent becomes 0 and next conditions where "RebuildStarted" event 
should be sent also aren't met:
             if (mse &&
                 st->percent == -1 &&
                 mse->percent >= 0)
                 alert("RebuildStarted", dev, NULL, mailaddr, mailfrom, 
alert_cmd, dosyslog);

Probably it is fine because rebuild already started and this is what 
monitor reads from /proc/mdstat. Shouldn't it return "NewArray" event 
instead those two "RebuildFinished" and "RebuildStarted" in this situation?

We use mdadm version 2.5.6 and monitor runs as a daemon with 10s 
interval and scan option.

Do we need to restart mdadm monitor when new disk is added to the system 
(hotplug)? Do we need to generate config file in such situation or 
running mdadm with option --scan is sufficient?

-- 
Best regards
Arkadiusz Bubała
Open-E Poland Sp. z o.o.
www.open-e.com

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