update a running busybox

[Denys Vlasenko]

On Tue, Mar 29, 2011 at 5:32 PM, Harald Becker <ralda at gmx.de> wrote:
>  Hallo Arno!
>
>> mount -r -o remount /
>> reboot
>>
>> The problem is, I can't remount it r/o. "device is busy".
>> And without doing this, my jffs2-filesystem is not in a stable state
>> while reboot.
>
> Do a lazy umount before reboot (umount -l). My approch:
>
> sync; sleep 0.25s
> killall5 -TERM
> sync; sleep 1.5s
> ...

Better approach is to parallelize initial sync and kill:

sync &
killall5 -TERM
sync; sleep 1.5s

Otherwise the "sync; sleep 0.25s" line may end up waiting
for a very long time if you have tons of dirty data in RAM.

If you run swap in background and immediately signal
everyone to TERMinate, then

(1) sync starts to free up memory occupied by dirty data

(2) processes terminating due to "killall5 -TERM" might (a)
delete some temporary files for which they have buffered
dirty data, thus "cancelling" writeout for it, and (b)
by exiting, they might free up useful RAM needed
for faster termination of other processes (say, big,
swapped out ones). Which in turn again may reduce
amount of swap activity.

> sync; sleep 0.25s
> sync; sleep 0.5s

Double sync is not needed, but you might want to have it
simply because of paranoid reasons
(every good admin should be a bit paranoid) :D

-- 
vda