On 6/22/20 4:51 AM, Naresh Kamboju wrote:
On Fri, 8 May 2020 at 12:23, Michael Ellerman mpe@ellerman.id.au wrote:
It is Very Rude to clear dmesg in test scripts. That's because the script may be part of a larger test run, and clearing dmesg potentially destroys the output of other tests.
We can avoid using dmesg -c by saving the content of dmesg before the test, and then using diff to compare that to the dmesg afterward, producing a log with just the added lines.
Signed-off-by: Michael Ellerman mpe@ellerman.id.au
tools/testing/selftests/lkdtm/run.sh | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/lkdtm/run.sh b/tools/testing/selftests/lkdtm/run.sh index dadf819148a4..0b409e187c7b 100755 --- a/tools/testing/selftests/lkdtm/run.sh +++ b/tools/testing/selftests/lkdtm/run.sh @@ -59,23 +59,25 @@ if [ -z "$expect" ]; then expect="call trace:" fi
-# Clear out dmesg for output reporting -dmesg -c >/dev/null
- # Prepare log for report checking
-LOG=$(mktemp --tmpdir -t lkdtm-XXXXXX) +LOG=$(mktemp --tmpdir -t lkdtm-log-XXXXXX) +DMESG=$(mktemp --tmpdir -t lkdtm-dmesg-XXXXXX) cleanup() {
rm -f "$LOG"
rm -f "$LOG" "$DMESG"+# Save existing dmesg so we can detect new content below +dmesg > "$DMESG"
# Most shells yell about signals and we're expecting the "cat" process # to usually be killed by the kernel. So we have to run it in a sub-shell # and silence errors. ($SHELL -c 'cat <(echo '"$test"') >'"$TRIGGER" 2>/dev/null) || true
# Record and dump the results
-dmesg -c >"$LOG" +dmesg | diff --changed-group-format='%>' --unchanged-group-format='' "$DMESG" - > "$LOG" || true
We are facing problems with the diff `=%>` part of the option. This report is from the OpenEmbedded environment. We have the same problem from livepatch_testcases.
# selftests lkdtm BUG.sh lkdtm: BUG.sh_ # # diff unrecognized option '--changed-group-format=%>' unrecognized: option_'--changed-group-format=%>' # # BusyBox v1.27.2 (2020-03-30 164108 UTC) multi-call binary. v1.27.2: (2020-03-30_164108 # # : _ # # Usage diff [-abBdiNqrTstw] [-L LABEL] [-S FILE] [-U LINES] FILE1 FILE2 diff: [-abBdiNqrTstw]_[-L # # BUG missing 'kernel BUG at' [FAIL]
Full test output log, https://qa-reports.linaro.org/lkft/linux-next-oe/build/next-20200621/testrun...
D'oh! Using diff's changed/unchanged group format was a nice trick to easily fetch the new kernel log messages.
I can't think of any simple alternative off the top of my head, so here's a kludgy tested-once awk script:
SAVED_DMESG="$(dmesg | tail -n1)" ... tests ... NEW_DMESG=$(dmesg | awk -v last="$SAVED_DMESG" 'p; $0 == last{p=1}')
I think timestamps should make each log line unique, but this probably won't handle kernel log buffer overflow.
Maybe it would be easier to log a known unique test delimiter msg and then fetch all new messages after that?
-- Joe