Messages in this thread | | | Date | Sun, 7 Apr 2024 15:52:52 -0700 | From | Bjorn Andersson <> | Subject | Re: Bug 218665 - nohz_full=0 prevents kernel from booting |
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On Tue, Apr 02, 2024 at 10:17:16AM +0200, Linux regression tracking (Thorsten Leemhuis) wrote: > Hi, Thorsten here, the Linux kernel's regression tracker. > > I noticed a regression report in bugzilla.kernel.org. As many (most?) > kernel developers don't keep an eye on it, I decided to forward it by mail. > > Tejun, apparently it's cause by a change of yours. > > Note, you have to use bugzilla to reach the reporter, as I sadly[1] can > not CCed them in mails like this. > > Quoting from https://bugzilla.kernel.org/show_bug.cgi?id=218665 : > > > booting the current kernel (6.9.0-rc1, master/712e1425) on x86_64 > > with nohz_full=0 cause a page fault and prevents the kernel from > > booting. > > > > Steps to reproduce: > > - make defconfig > > - set CONFIG_NO_HZ_FULL=y > > - set CONFIG_SUSPEND=n and CONFIG_HIBERNATION=n (to get CONFIG_PM_SLEEP_SMP=n) > > - make > > - qemu-system-x86_64 -nographic -cpu qemu64 -smp cores=2 -m 1024 -kernel arch/x86/boot/bzImage -append "earlyprintk=ttyS0 console=ttyS0 root=/dev/dummy rootwait nohz_full=0" > > > > I have attached the output of a failed nohz_full=0 boot as > > nohz_full_0.txt and - for reference - the output of a nohz_full=1 > > boot as nohz_full_1.txt. > > > > Interestingly enough, using the deprecated isolcpus parameter to > > enable NO_HZ for cpu0 works. I've attached the output as > > isolcpus_nohz_0.txt. > > > > Bisecting showed 5797b1c18919cd9c289ded7954383e499f729ce0 as first bad commit. > > See the ticket for more details. > > Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) > -- > Everything you wanna know about Linux kernel regression tracking: > https://linux-regtracking.leemhuis.info/about/#tldr > If I did something stupid, please tell me, as explained on that page. > > [1] because bugzilla.kernel.org tells users upon registration their > "email address will never be displayed to logged out users" > > #regzbot introduced: 5797b1c18919cd9c289ded7954383e499f729ce0 > #regzbot from: Friedrich Oslage > #regzbot duplicate https://bugzilla.kernel.org/show_bug.cgi?id=218665 > #regzbot title: workqueue: nohz_full=0 prevents booting > #regzbot ignore-activity
In addition to this report, I have finally bisected another regression to the same commit:
I start neovim, send SIGSTOP (i.e. ^Z) to it, start another neovim instance and upon sending SIGSTOP to that instance all of userspace locks up - 100% reproducible.
The kernel seems to continue to operate, and tapping the power button dislodge the lockup and I get a clean shutdown.
This is seen on multiple Arm64 (Qualcomm) machines with upstream defconfig since commit '5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues")'.
Regards, Bjorn
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