From: "Paul E. McKenney" <paulmck@kernel.org>
To: Daniel Axtens <dja@axtens.net>
Cc: rcu@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, mark.rutland@arm.com
Subject: Re: powerpc 5.10-rcN boot failures with RCU_SCALE_TEST=m
Date: Fri, 27 Nov 2020 07:50:22 -0800 [thread overview]
Message-ID: <20201127155022.GV1437@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <87eekfh80a.fsf@dja-thinkpad.axtens.net>
On Fri, Nov 27, 2020 at 01:02:29PM +1100, Daniel Axtens wrote:
> Hi all,
>
> I'm having some difficulty tracking down a bug.
>
> Some configurations of the powerpc kernel since somewhere in the 5.10
> merge window fail to boot on some ppc64 systems. They hang while trying
> to bring up SMP. It seems to depend on the RCU_SCALE/PERF_TEST option.
> (It was renamed in the 5.10 merge window.)
Adding Mark Rutland on CC in case his similarly mystifying experience
obtaining a fix for ARM has relevance. From what I could see, that
was a delayed consequence of the x86/entry rewrite. It was similarly
difficult to bisect.
Thanx, Paul
> I can reproduce it as follows with qemu tcg:
>
> make -j64 pseries_le_defconfig
> scripts/config -m RCU_SCALE_TEST
> scripts/config -m RCU_PERF_TEST
> make -j 64 vmlinux CC="ccache gcc"
>
> qemu-system-ppc64 -cpu power9 -M pseries -m 1G -nographic -vga none -smp 4 -kernel vmlinux
>
> ...
> [ 0.036284][ T0] Mount-cache hash table entries: 8192 (order: 0, 65536 bytes, linear)
> [ 0.036481][ T0] Mountpoint-cache hash table entries: 8192 (order: 0, 65536 bytes, linear)
> [ 0.148168][ T1] POWER9 performance monitor hardware support registered
> [ 0.151118][ T1] rcu: Hierarchical SRCU implementation.
> [ 0.186660][ T1] smp: Bringing up secondary CPUs ...
> <hangs>
>
> I have no idea why RCU_SCALE/PERF_TEST would be causing this, but that
> seems to be what does it: if I don't set that, the kernel boots fine.
>
> I've tried to git bisect it, but I keep getting different results:
> always a random merge of a seemingly-unrelated subsystem tree - things
> like armsoc or integrity or input.
>
> It appears to also depend on the way the kernel is booted. Testing with
> a Canonical kernel, so a slightly different config but including
> RCU_SCALE_TEST=m, I see:
>
> Power8 host + KVM + grub -> boots
> Power9 host bare metal (kexec) -> fails
> Power9 host + KVM + grub -> fails
> Power9 host + KVM + qemu -kernel -> boots
> qemu TCG + power9 cpu -> fails
> qemu TCG + power8 cpu -> fails
>
> Any ideas?
>
> Kind regards,
> Daniel
>
> $ qemu-system-ppc64 -version
> QEMU emulator version 4.2.1 (Debian 1:4.2-3ubuntu6.9)
>
> $ gcc --version
> gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
>
> It also happens when compiling with GCC 7 and 10.
>
>
next prev parent reply other threads:[~2020-11-27 15:50 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-27 2:02 powerpc 5.10-rcN boot failures with RCU_SCALE_TEST=m Daniel Axtens
2020-11-27 15:50 ` Paul E. McKenney [this message]
2020-11-27 16:41 ` Uladzislau Rezki
2020-12-02 14:03 ` Michael Ellerman
2020-12-02 14:39 ` Uladzislau Rezki
2020-12-03 6:22 ` Michael Ellerman
2020-12-03 14:34 ` Uladzislau Rezki
2020-12-04 20:23 ` Uladzislau Rezki
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