Hi, we were about to switch on LTO by default on Ubuntu 21.04. While doing so I was made aware of a related test breakage on s390x.
Components Chrony: 4.0-5ubuntu2 Gcc: 4:10.2.0-1ubuntu1 Glibc: 2.33-0ubuntu2 For the test, chrony is rebuilt which now started to pick up LTO being enabled. Most of the tests actually worked, so it is no general all-goes-to-h... problem But when running the simulation tests it failed case 110. Reprocuced in a s390x LXD container: $ apt update $ apt build-dep chrony $ apt source chrony $ cd chrony-4.0 $ ./debian/rules build $ mkdir /tmp/mytest/ $ export AUTOPKGTEST_TMP=/tmp/mytest/ $ export CLKNETSIM_PATH=/tmp/mytest/ $ cd test/simulation $ ./110-chronyc Looking into that I had I found that 110 has quite a subset of tests All of them worked until this one: network with 1*0 servers and 1 clients: non-default settings: chronyc_conf=dns -n dns +n dns -4 dns -6 dns -46 timeout 200 retries 1 keygen keygen 10 MD5 128 keygen 11 MD5 40 help quit nosuchcommand chronyc_start=0 dns=1 limit=1 refclock_jitter=1e-4 server_conf=server 192.168.123.1 server_strata=0 starting node 1: OK starting node 2: OK running simulation:clknetsim failed ERROR FAIL After eliminating a bunch of red herrings I've found that when I trigger that I get a user space fault in dmesg like: [2680568.517156] Last Breaking-Event-Address: [2680568.517159] [<000002aa2e603214>] 0x2aa2e603214 [2684266.007865] User process fault: interruption code 003b ilc:2 in libc-2.33.so[3ff8f480000+1c5000] [2684266.007878] Failing address: 00000000d1230000 TEID: 00000000d1230800 [2684266.007880] Fault in primary space mode while using user ASCE. [2684266.007882] AS:00000006dd8341c7 R3:0000000000000024 [2684266.007887] CPU: 21 PID: 798868 Comm: chronyc Tainted: P O 5.4.0-66-generic #74-Ubuntu [2684266.007888] Hardware name: IBM 2964 N63 400 (LPAR) [2684266.007890] User PSW : 0705100180000000 000003ff8f5b4620 [2684266.007892] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:1 AS:0 CC:1 PM:0 RI:0 EA:3 [2684266.007894] User GPRS: 0000000000000000 0000000000000015 00000000ffffffff 0000000000000200 [2684266.007895] 0000000000000001 0000000000000014 00000000d1230123 000003fff087c930 [2684266.007896] 0000000000000014 0000000000000014 00000000d1230123 0000000000000001 [2684266.007897] 000003ff8fa2cf98 000002aa2b3971f0 000002aa2b387efc 000003fff087c7d0 [2684266.007905] User Code: 000003ff8f5b460e: ec1200762065 clgrj %r1,%r2,2,000003ff8f5b46fa 000003ff8f5b4614: ec93007f2065 clgrj %r9,%r3,2,000003ff8f5b4712 #000003ff8f5b461a: ec980050007c cgij %r9,0,8,000003ff8f5b46ba >000003ff8f5b4620: 9180a002 tm 2(%r10),128 000003ff8f5b4624: a7740025 brc 7,000003ff8f5b466e 000003ff8f5b4628: b24f0060 ear %r6,%a0 000003ff8f5b462c: e310a0880004 lg %r1,136(%r10) 000003ff8f5b4632: eb660020000d sllg %r6,%r6,32 [2684266.007920] Last Breaking-Event-Address: [2684266.007924] [<000002aa2b383214>] 0x2aa2b383214 I was able to confirm that disabling LTO resolved the issue, so for now that will stay disabled on s390x. But I wanted to ask here if chrony-experts could have a look at reproducing that if it makes any sense to you and if myber there could be a fix that then allows to enable LTO. FYI: See [1] for the related Ubuntu bug and the strange trip until I found it indeed was LTO. [1]: https://bugs.launchpad.net/ubuntu/+source/chrony/+bug/1921377 -- Christian Ehrhardt Staff Engineer, Ubuntu Server Canonical Ltd -- To unsubscribe email chrony-dev-requ...@chrony.tuxfamily.org with "unsubscribe" in the subject. For help email chrony-dev-requ...@chrony.tuxfamily.org with "help" in the subject. Trouble? Email listmas...@chrony.tuxfamily.org.