Messages in this thread | | | Date | Wed, 14 Jun 2023 11:21:58 +0200 | From | Peter Zijlstra <> | Subject | Re: printk.time causes rare kernel boot hangs |
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On Tue, Jun 13, 2023 at 02:41:05PM +0100, Richard W.M. Jones wrote: > [Being tracked in this bug which contains much more detail: > https://gitlab.com/qemu-project/qemu/-/issues/1696 ]
Can I please just get the detail in mail instead of having to go look at random websites?
> Recent kernels hang rarely when booted on qemu. Usually you need to > boot 100s or 1,000s of times to see the hang, compared to 292,612 [sic] > successful boots which I was able to do before the problematic commit. > > A reproducer (you'll probably need to use Fedora) is:
Debian only shop here... in fact, I still have machines without systemd.
> $ while guestfish -a /dev/null -v run >& /tmp/log; do echo -n . ; done > > You will need to leave it running for probably several hours, and > examine the /tmp/log file at the end. > > I tracked this down to the following commit: > > commit f31dcb152a3d0816e2f1deab4e64572336da197d > Author: Aaron Thompson <dev@aaront.org> > Date: Thu Apr 13 17:50:12 2023 +0000 > > sched/clock: Fix local_clock() before sched_clock_init() > > Have local_clock() return sched_clock() if sched_clock_init() has not > yet run. sched_clock_cpu() has this check but it was not included in the > new noinstr implementation of local_clock(). > > (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f31dcb152a3d0816e2f1deab4e64572336da197d) > > Reverting this commit fixes the problem. > > I don't know _why_ this commit is wrong, but can we revert it as it > causes serious problems with libguestfs hanging randomly. > > Or if there's anything you want me to try out then let me know, > because I can reproduce the problem locally quite easily.
Well, since it's virt and all, can you attach gdb to the gdb-stub and see where it's at? Any clue is better than no clue.
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