On 25 September 2026 12:45:27 BST, Joel Granados <[email protected]> wrote: >On Wed, Sep 23, 2026 at 04:53:54PM +0100, Bradley Morgan wrote: >> On 23 September 2026 15:49:37 BST, Zhan Xusheng ><[email protected]> >> wrote: >> >proc_int_k2u_conv_kop() returns the sign through *negp and the >magnitude >> >through *u_ptr. For a negative value it used to convert the >> >sign-extended int and negate afterwards, so the magnitude came back as >a >> >wrapped 64-bit number. Nothing noticed, because no test wrote a >> >negative value to a jiffies sysctl. >> > >> >Write one to each of the three int converters and require the value to >> >read back unchanged. Each value is chosen to convert exactly at every >> >CONFIG_HZ, so the test does not depend on it: >> > >> > converter write jiffies stored reads back >> > jiffies -1 -HZ -1 >> > ms_jiffies -1000 -HZ -1000 >> > userhz_jiffies -100 -HZ -100 >> > >> >On a kernel without the fix, at CONFIG_HZ=250: >> > >> > # int_jiffies: got '-18372957097414713411', want '-1' >> > # int_ms_jiffies: got '-18446744069414585320', want '-1000' >> > # int_userhz_jiffies: got '-18446742229035144346', want '-100' >> > not ok 1 test_int_jiffies_negative >> > >> >(paths shortened; the runner prints them under >> >/proc/sys/debug/test_sysctl) >> > >> >Signed-off-by: Zhan Xusheng <[email protected]> >> >--- >> > tools/testing/selftests/sysctl/sysctl.sh | 23 +++++++++++++++++++++++ >> > 1 file changed, 23 insertions(+) >> > >> >diff --git a/tools/testing/selftests/sysctl/sysctl.sh >b/tools/testing/selftests/sysctl/sysctl.sh >> >index ceb5cfa0cfd4..ad1ee0fccd7c 100755 >> >--- a/tools/testing/selftests/sysctl/sysctl.sh >> >+++ b/tools/testing/selftests/sysctl/sysctl.sh >> >@@ -328,6 +328,29 @@ test_int_plain() >> > assert_int_range "$t" "$baseline" || RET=$KSFT_FAIL >> > } >> > >> >+# The jiffies converters report the sign separately from the >magnitude, so a >> >+# negative value must survive the round trip through the converter. >Each >> >+# value below is chosen to convert exactly at every CONFIG_HZ. >> >> I have a feeling this could be decreased, but I don't care. > >If you don't care, don't comment. >>
its because I think it could, but it isn't a complete patch breaker. >> Reviewed-by: Bradley Morgan <[email protected]> >> >> >> Tested on PowerPC: >> >> Tested-by: Bradley Morgan <[email protected]> # POWER10 > >Please don't suffix anything after the tag as b4 picks it up. > >Best > --- Thanks! "I'm not a very positive person" - Linus torvalds
