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. > > 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
signature.asc
Description: PGP signature
