Hi Michael, Thanks for sharing the detailed analysis on this issue. Let me check this with the team here and from s390x core team, will keep you posted.
Thanks, -Dipak Zope From: Michael Tokarev <[email protected]> Date: Monday, 6 February 2023 at 6:59 PM To: [email protected] <[email protected]> Subject: [EXTERNAL] suspecting 5.10.0-21 kernel breaking something with futexes on s390x #1030545 reported against qemu. The issue is rather fundamental for qemu, it is one of the very basic operations. I can reproduce the same issue on older versions as well, even installed bullseye chroot on zelenka.d.o and it fails/hangs the same way there. A common pattern is the usage of 5.10.0-21 kernel. For example, last successful builds of libguestfs (which suffered from this issue) were done on hosts running previous kernel version, and there's no single successful build on 5.10.0-21. Zelenka is also running 5.10.0-21, - I asked to reboot it into -20 to see if it changes something. We tried to run it on other s390x machines, - the bug does not show itself there. But these run other kernels. I looked at the changes between -20 and -21, 5.10.150 -> 5.10.162, and I do see at least one s390x-specific change to futexes (and it is the futex which behave in a weird way now), plus changes in signal/wakeup handling. Also, there are other changes past .162 which includes quite some changes to s390x atomix/cmpxchg stuff. So it *might* be related. At any rate, with the data points I have so far, everything points to the kernel. If anyone know what's going on there, please do share your knowledge :) Thanks, /mjt
