Re: Linux 5.14

[Guenter Roeck <linux@roeck-us.net>]

On Sun, Aug 29, 2021 at 03:19:23PM -0700, Linus Torvalds wrote:
> So I realize you must all still be busy with all the galas and fancy
> balls and all the other 30th anniversary events, but at some point you
> must be getting tired of the constant glitz, the fireworks, and the
> champagne. That ball gown or tailcoat isn't the most comfortable
> thing, either. The celebrations will go on for a few more weeks yet,
> but you all may just need a breather from them.
> 
> And when that happens, I have just the thing for you - a new kernel
> release to test and enjoy. Because 5.14 is out there, just waiting for
> you to kick the tires and remind yourself what all the festivities are
> about.
> 
> Of course, the poor tireless kernel maintainers won't have time for
> the festivities, because for them, this just means that the merge
> window will start tomorrow. We have another 30 years to look forward
> to, after all. But for the rest of you, take a breather, build a
> kernel, test it out, and then you can go back to the seemingly endless
> party that I'm sure you just crawled out of.
> 

Build results:
	total: 154 pass: 154 fail: 0
Qemu test results:
	total: 479 pass: 479 fail: 0

So far so good, but there is a brand new runtime warning, seen when booting
s390 images.

[    3.218816] ------------[ cut here ]------------
[    3.219010] WARNING: CPU: 1 PID: 0 at kernel/sched/core.c:5779 sched_core_cpu_starting+0x172/0x180
[    3.219548] Modules linked in:
[    3.219948] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.14.0 #1
[    3.220139] Hardware name: QEMU 2964 QEMU (KVM/Linux)
[    3.220312] Krnl PSW : 0400e00180000000 0000000000186e86 (sched_core_cpu_starting+0x176/0x180)
[    3.220593]            R:0 T:1 IO:0 EX:0 Key:0 M:0 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3
[    3.220746] Krnl GPRS: 0000000000000000 0000000000000200 0000000000000200 0000000000000200
[    3.220821]            ffffffffffffffff 0000000000000000 000000000161f300 0000000001209c30
[    3.220893]            0000000000000002 00000000019bf418 0000000000000001 000000001fbf2300
[    3.220964]            0000000000000000 0000000000000001 0000000000186dc4 0000038000093c90
[    3.222032] Krnl Code: 0000000000186e7a: af000000		mc	0,0
[    3.222032]            0000000000186e7e: a7f4ff88		brc	15,0000000000186d8e
[    3.222032]           #0000000000186e82: af000000		mc	0,0
[    3.222032]           >0000000000186e86: a7f4ffe7		brc	15,0000000000186e54
[    3.222032]            0000000000186e8a: 0707		bcr	0,%r7
[    3.222032]            0000000000186e8c: 0707		bcr	0,%r7
[    3.222032]            0000000000186e8e: 0707		bcr	0,%r7
[    3.222032]            0000000000186e90: c00400000000	brcl	0,0000000000186e90
[    3.222845] Call Trace:
[    3.222992]  [<0000000000186e86>] sched_core_cpu_starting+0x176/0x180
[    3.223114] ([<0000000000186dc4>] sched_core_cpu_starting+0xb4/0x180)
[    3.223182]  [<00000000001963e4>] sched_cpu_starting+0x2c/0x68
[    3.223243]  [<000000000014f288>] cpuhp_invoke_callback+0x318/0x970
[    3.223304]  [<000000000014f970>] cpuhp_invoke_callback_range+0x90/0x108
[    3.223364]  [<000000000015123c>] notify_cpu_starting+0x84/0xa8
[    3.223426]  [<0000000000117bca>] smp_init_secondary+0x72/0xf0
[    3.223492]  [<0000000000117846>] smp_start_secondary+0x86/0x90
[    3.223614] no locks held by swapper/1/0.
[    3.223713] Last Breaking-Event-Address:
[    3.223762]  [<0000000000000000>] 0x0
[    3.224578] random: get_random_bytes called from __warn+0x11e/0x158 with crng_init=0
[    3.234056] ---[ end trace 5ffbc0f4ab37cea9 ]---

Commit 3c474b3239f12 ("sched: Fix Core-wide rq->lock for uninitialized
CPUs") sems to be the culprit. Indeed, the warning is gone after reverting
this commit.

Guenter