On Tue 24-04-18 11:50:28, Joe Lawrence wrote:
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 ]]; thendie "failed to unload module $mod (refcnt)"fisleep $RETRY_INTERVAL- done
The repeating pattern of "while <some test>; do <count>; if <count beyond max retries>; then <die>..." seems to ask for encapsulation.
Yeah I definitely agree. I think at some point I had acquired bash-fatigue; I wasn't sure how to cleanly wrap <some test> around that extra logic. In C, I could do something clever with macros or a callback function. My bash scripting isn't great, so I copied and pasted my way through it. Suggestions welcome.
Okay, here's what I came up with... first off, do you prefer this kind of transition check vs. looking only at a specific module?
# check_transition() - verify that no livepatch transition in effect function check_transition() { grep -q '^1$' /sys/kernel/livepatch/*/transition 2>/dev/null }
Elegant!
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" }
My idea was to make the die() part of the retry loop. This implementation is, however, more flexible.
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.
I think check_*() functions can be avoided for trivial tests. retry_cmd() can be passed a more complex command string than a single function name.
Regarding naming, I'd say wait_false() or similar would better describe what retry_cmd() does.
Libor