linux-kernel - Re: Regression due to 7ff9554 "printk: convert byte-buffer to variable-length record buffer"

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Message-ID: <CAPXgP10510MCgro77-sOVjvvooa5J5=0c_FR1-QbuN9smLdBPw@mail.gmail.com>
Date:	Thu, 10 May 2012 22:15:14 +0200
From:	Kay Sievers <kay@...y.org>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	William Douglas <william.douglas@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-next@...r.kernel.org
Subject: Re: Regression due to 7ff9554 "printk: convert byte-buffer to
 variable-length record buffer"

On Thu, May 10, 2012 at 10:13 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 05/10/2012 02:09 PM, Stephen Warren wrote:
>> On 05/10/2012 02:06 PM, Kay Sievers wrote:
>>> On Thu, May 10, 2012 at 9:54 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>>>> On 05/09/2012 12:31 PM, Stephen Warren wrote:
>>>>> For me, next-20120508 prints nothing when booted, and I think also
>>>>> hangs. To solve this, I reverted:
>>>>>
>>>>> 7ff9554 printk: convert byte-buffer to variable-length record buffer
>>>>>
>>>>> In order to build, I also had to revert:
>>>>>
>>>>> c4e00da driver-core: extend dev_printk() to pass structured data
>>>>>
>>>>> Note: I'm running on an ARM system using a serial console, with
>>>>> earlyprintk enabled.
>>>>
>>>> This issue still occurs in next-20120510.
>>>>
>>>> I've tracked it down to the assignment of msg->ts_nsec near the end of
>>>> log_store(). If I comment this out, everything works. The problem is the
>>>> assignment, not the call to local_clock():
>>>>
>>>> fails:
>>>>        msg->ts_nsec = local_clock();
>>>> fails:
>>>>        msg->ts_nsec = 0;//local_clock();
>>>> works:
>>>>        //msg->ts_nsec = local_clock();
>>>
>>> Weird.
>>>
>>> What happens if you change it to:
>>>   cpu_clock(logbuf_cpu);
>>> ?
>>>
>>> If it works, the timestamps look ok?
>>
>> I doubt that would work - after all, assigning 0 fails, but not
>> performing the assignment at all works. But, I'll go try it...
>
> Calling cpu_clock() instead of local_clock() fails in the same way.

Ok, didn't really see the assign to 0 you tried, sorry. :)

And 'dmesg' works when you run the box with the line commented out?

And 'cat /dev/kmsg'?

Kay
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