linux-kernel - Re: r8169: disable ASPM during NAPI poll locking changes --> BUG: Invalid wait context --> PREEMPT

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Message-ID: <59e86f97-3e77-14e0-948a-1a87ccf72f36@gmail.com>
Date:   Mon, 22 May 2023 12:32:38 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Mike Galbraith <efault@....de>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: r8169: disable ASPM during NAPI poll locking changes --> BUG:
 Invalid wait context --> PREEMPT_RT pain

On 22.05.2023 10:06, Sebastian Andrzej Siewior wrote:
> On 2023-05-21 16:27:10 [+0200], Mike Galbraith wrote:
>> On Sun, 2023-05-21 at 08:03 +0200, Mike Galbraith wrote:
>>> Greetings,
>>>
>>> The locks added to prep for $subject induce invalid context moaning due
>>> to not being raw locks, but if I do that, the hold time does very bad
>>> things to RT.
>>
>> The locks aren't really 160us horrible. The GPU was enabled (oops),
>> nouveau then makes box horrible for RT (and graphics:).  With GPU
>> turned back off, the largest trace I saw was 77us, which jibes pretty
>> well with new max of low to mid 50s without ftrace running, or up a tad
>> over 20us for this now pretty old commodity i7 desktop box.
> 
> So you are saying it is all good?
> I've been looking at the r8169 the other day and it seemed all good
> since it was only scheduling workqueues and NAPI. But now I see this
> mac_ocp_lock + config25_lock which are acquire in hardirq context but
> can't. This needs to be taken care.

What do you mean with "but can't"? Taking a spinlock in hardirq context
is normal.

> 
>> 	-Mike
> 
> Sebastian