Re: Boot stall regression from "printk for 5.19" merge

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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On Mon, 20 Jun 2022, Petr Mladek wrote:

> Resending with Ilpo, driver maintainer, in CC.
> 
> On Mon 2022-06-20 13:44:17, Petr Mladek wrote:
> > On Mon 2022-06-20 11:29:36, Marek Behún wrote:
> > > On Mon, 20 Jun 2022 00:29:16 +0206
> > > John Ogness <john.ogness@linutronix.de> wrote:
> > > > On 2022-06-19, Marek Behún <kabel@kernel.org> wrote:
> > > > > causes a regression on arm64 (Marvell CN9130-CRB board) where the
> > > > > system boot freezes in most cases (and is unusable until restarted by
> > > > > watchdog), or, in some cases boots, but the console output gets mangled
> > > > > for a while (the serial console spits garbage characters).  
> > > 
> > > attaching bootlogs and config.
> > 
> > This is the log when the system booted:
> > 
> > > [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd083]
> > > [    0.000000] Linux version 5.19.0-rc2-00410-g9776fe0f424b (kabel@dellmb) (aarch64-unknown-linux-gnu-gcc (Gentoo Hardened 10.3.1_p20211126 p0) 10.3.1 20211126, GNU ld (Gentoo 2.37_p1 p2) 2.37) #491 SMP Mon Jun 20 11:00:54 CEST 2022
> > > [    0.000000] Machine model: Marvell Armada CN9130-CRB-B
> > > [    0.000000] earlycon: uart8250 at MMIO32 0x00000000f0512000 (options '')
> > > [    0.000000] printk: bootconsole [uart8250] enabled
> > 
> > Early console enabled.
> > 
> > > [    0.000000] NUMA: No NUMA configuration found
> > [...]
> > > [    0.062565] rcu: Hierarchical SRCU implementation.
> > > [    0.062589] printk: bootconsole [uart8250] printing thread started
> > 
> > The early console started being handled by the kthread.
> > 
> > > [    0.073843] smp: Bringing up secondary CPUs ...
> > > [    0.074238] Detected PIPT I-cache on CPU1
> > [...]
> > > [    1.067359] io scheduler kyber registered
> > > [    1.120214] armada-ap806-pinctrl f06f4000.system-controller:pinctrl: registered pinctrl driver
> > > [    1.120577] armada-cp110-pinctrl f2440000.system-controller:pinctrl: registered pinctrl driver
> > > [    1.137980] mv_xor_v2 f0400000.xor: Marvell Version 2 XOR driver
> > > [    1.166562] printk:[ console [ttyS0] printing thread started
> > >  [    1.166564] printk: console [ttyS0] enabled
> > 
> > 2nd console was added using the properly initialized serial port.
> > It should use the same physical port as the early console.
> > 
> > Both early console and proper console driver has its own kthread.
> > 
> > >    1.166486] f0512000.serial: ttyS0 at MMIO 0xf0512000 (irq = 22, base_baud = 12500000) is a 16550A
> > 
> > The line is malformed. I wonder if both early console and proper
> > console used the same port in parallel.
> > 
> > > [    1.166567] printk: bootconsole [uart8250] disabled
> > > [    1.185422] printk: bootconsole [uart8250] printing thread stopped
> > 
> > The early console was disabled. Only the properly initialized serial
> > console is used. All should be fine now.
> > 
> > 
> > > [    1.188773] brd: module loaded
> > > [    1.190567] loop: module loaded
> > [...]
> > > [    5.316958] Freeing unused kernel memory: 2752K
> > > [    5.364349] Run /sbin/init as init process
> > 
> > And I did not catch any further problem.
> > 
> > So, it looks like that con->write() code is not correctly serialized
> > between the early and normal console.
> > 
> > 
> > Now, let's see the last lines of failing logs:
> > 
> > 
> > > [    1.071214] io scheduler kyber registered
> > > [    1.124272] armada-ap806-pinctrl f06f4000.system-controller:pinctrl: registered pinctrl driver
> > > [
> > 
> > > [    1.067314] io scheduler kyber registered
> > > [    1.120226] armada-ap806-pinctrl f06f4000.system-controller:pinctrl: registered pinctrl driver
> > > [    1.120603] armada-cp110-pinctrl f2440000.system-controller:pinctrl: registered pinctrl driver
> > > [    1.137975] mv_xor_v2 f0400000.xor: Marvell Version 2 XOR driver
> > > [    1.138248] mv_xor_v2 f0420000.xor: Marvell Version 2 XOR driver
> > > [    1.
> > 
> > > [    1.067214] io scheduler kyber registered
> > > [    1.120098] armada-ap806-pinctrl f06f4000.system-controller:pinctrl: registered pinctrl driver
> > > [    1.120466] armada-cp110-pinctrl f2440000.system-controller:pinctrl: registered pinctrl driver
> > > [    1.137871] mv_xor_v2 f0400000.xor: Marvell Version 2 XOR driver
> > > [    1.138160] mv_xor_v2 f0420000.xor: Marvell Version 2 XOR driver
> > > [
> > 
> > All three logs end in the middle of a line. If you compare it with the
> > "working" log then the end 1-3 lines before the normal console was added.
> > 
> > The console output might is delayed because of the threads. Most
> > likely, the output ended when both early and normal console driver
> > started to use the same port.
> > 
> > I am going to check the driver...

Perhaps try reverting 8f3631f0f6eb ("serial/8250: Use fifo in 8250 
console driver") if there's yet another unexplored corner hit.

-- 
 i.