On 04/23/2018 10:43 AM, Joe Lawrence wrote:
> On Fri, Apr 20, 2018 at 02:56:05PM +0200, Libor Pechacek wrote:
>> On Thu 12-04-18 10:54:31, Joe Lawrence wrote:
>>> + fi
>>> + echo "$ret" > /dev/kmsg
>>> +}
>>> +
>>> +# unload_mod(modname) - unload a kernel module
>>> +# modname - module name to unload
>>> +function unload_mod() {
>>> + local mod="$1"
>>> +
>>> + # Wait for module reference count to clear ...
>>> + local i=0
>>> + while [[ $(cat /sys/module/"$mod"/refcnt) != "0" ]]; do
>>> + i=$((i+1))
>>> + if [[ $i -eq $MAX_RETRIES ]]; then
>>> + die "failed to unload module $mod (refcnt)"
>>> + fi
>>> + sleep $RETRY_INTERVAL
>>> + done
>>
>> The repeating pattern of "while <some test>; do <count>; if <count beyond max
>> retries>; then <die>..." seems to ask for encapsulation.
>>
>
> Yeah I definitely agree. I think at some point I had acquired
> bash-fatigue; I wasn't sure how to cleanly wrap <some test> around that
> extra logic. In C, I could do something clever with macros or a
> callback function. My bash scripting isn't great, so I copied and
> pasted my way through it. Suggestions welcome.
>
Okay, here's what I came up with... first off, do you prefer this kind
of transition check vs. looking only at a specific module?
# check_transition() - verify that no livepatch transition in effect
function check_transition() {
grep -q '^1$' /sys/kernel/livepatch/*/transition 2>/dev/null
}
then wrap the retry/timeout logic like:
# retry_cmd(cmd) - loop a command until it is successful or
# $MAX_RETRIES, sleeping $RETRY_INTERVAL in
# between tries
# cmd - command and its arguments to run
function retry_cmd() {
local cmd="$*"
local i=0
while eval "$cmd"; do
i=$((i+1))
[[ $i -eq $MAX_RETRIES ]] && return 1
sleep $RETRY_INTERVAL
done
return 0
}
and the callers to something like:
# wait_for_transition() - wait until all livepatch transitions clear
function wait_for_transition() {
retry_cmd check_transition ||
die "failed to complete transition"
}
I can create similar check() functions to eval for sysfs file existence,
file content, reference count, etc. to remove all the other
retry/timeout loops.
Regards,
-- Joe
