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From: Julien Grall <julien.grall@arm.com>
To: John Ogness <john.ogness@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-rt-users <linux-rt-users@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Dave P Martin <Dave.Martin@arm.com>
Subject: Re: [ANNOUNCE] v5.0.3-rt1
Date: Tue, 26 Mar 2019 10:26:31 +0000	[thread overview]
Message-ID: <28ab7caf-1ada-1c39-c2f9-cd69b2376ef8@arm.com> (raw)
In-Reply-To: <87imw7qm2p.fsf@linutronix.de>

Hi John,

On 3/25/19 10:34 AM, John Ogness wrote:
> On 2019-03-25, Julien Grall <julien.grall@arm.com> wrote:
>> [...]
>> [    1.169151] 002: Serial: AMBA PL011 UART driver
>> [    1.254891] 002: 7ff80000.uart: ttyAMA0 at MMIO 0x7ff80000 (irq = 32, base_baud = 0) is a PL011 rev3
>> [    1.255007] 002: printk: console [ttyAMA0] enabled
> 
> The ttyAMA drivers do not have support for atomic printing, so it is not
> the new atomic feature that is causing the mangling. For your setup, all
> printk console printing is being handled within a specific context, the
> printk kernel thread.

This series is somehow making worst when using ttyAMA0. I haven't see 
any mangling with 4.19-rt.

> 
> It looks to me like some userspace application (systemd?) is writing
> directly to /dev/ttyAMA0. If the kernel is also writing to this device
> (because it is setup as a console), then the output will be
> mangled. There is no high-level synchronization between console output
> and directly writing to UART devices. Maybe you need to set your
> loglevel so that the kernel does not do the printing? For example,
> loglevel=1?

I am a bit confused with your suggestion. This would basically means I 
would not be able to see kernel warning. So this would impair any 
development on Linux-rt.

> 
> You should see this problem with older kernel versions as well.

I have tried with 4.19-rt and didn't see a similar issue. The trace 
comes pretty clean in one go. With 5.0-rt, the trace never come clean.

Cheers,

-- 
Julien Grall

  reply	other threads:[~2019-03-26 10:26 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-20 17:15 Sebastian Andrzej Siewior
2019-03-22 18:52 ` Julien Grall
2019-03-25  8:13   ` John Ogness
2019-03-25 10:18     ` Julien Grall
2019-03-25 10:34       ` John Ogness
2019-03-26 10:26         ` Julien Grall [this message]
2019-03-26 16:04           ` John Ogness
2019-03-27 18:33 ` [PATCH 1/4] printk: An all-in-one commit to fix build failures Sebastian Andrzej Siewior
2019-03-27 18:33   ` [PATCH 2/4] powerpc/stackprotector: work around stack-guard init from atomic Sebastian Andrzej Siewior
2019-05-10 21:46     ` Steven Rostedt
2019-03-27 18:33   ` [PATCH 3/4] powerpc/pseries/iommu: Use a locallock instead local_irq_save() Sebastian Andrzej Siewior
2019-03-27 18:33   ` [PATCH 4/4] powerpc: reshuffle TIF bits Sebastian Andrzej Siewior

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