linux-kernel - Re: [stable] [PATCH 1/2] coresight: etb10: Do not call smp_processor

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Date:   Wed, 15 Jan 2020 17:28:19 +0000
From:   Suzuki Kuruppassery Poulose <suzuki.poulose@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Sasha Levin <sashal@...nel.org>, stable@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, mathieu.poirier@...aro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [stable] [PATCH 1/2] coresight: etb10: Do not call
 smp_processor_id from preemptible

On 15/01/2020 17:21, Greg KH wrote:
> On Wed, Jan 15, 2020 at 04:44:29PM +0000, Suzuki Kuruppassery Poulose wrote:
>>
>> Hi Greg,
>>
>> On 15/01/2020 15:11, Greg KH wrote:
>>> On Thu, Jan 09, 2020 at 02:36:17PM +0000, Suzuki Kuruppassery Poulose wrote:
>>>> On 09/01/2020 14:35, Sasha Levin wrote:
>>>>> On Wed, Jan 08, 2020 at 11:05:40AM +0000, Suzuki K Poulose wrote:
>>>>>> [ Upstream commit 730766bae3280a25d40ea76a53dc6342e84e6513 ]
>>>>>>
>>>>>> During a perf session we try to allocate buffers on the "node" associated
>>>>>> with the CPU the event is bound to. If it is not bound to a CPU, we
>>>>>> use the current CPU node, using smp_processor_id(). However this is
>>>>>> unsafe
>>>>>> in a pre-emptible context and could generate the splats as below :
>>>>>>
>>>>>> BUG: using smp_processor_id() in preemptible [00000000] code: perf/2544
>>>>>>
>>>>>> Use NUMA_NO_NODE hint instead of using the current node for events
>>>>>> not bound to CPUs.
>>>>>>
>>>>>> Fixes: 2997aa4063d97fdb39 ("coresight: etb10: implementing AUX API")
>>>>>> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
>>>>>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>>>>>> Cc: stable <stable@...r.kernel.org> # v4.9 to v4.19
>>>>>> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
>>>>>> Link: https://lore.kernel.org/r/20190620221237.3536-5-mathieu.poirier@linaro.org
>>>>>>
>>>>>
>>>>> I've queued this for 4.9-4.19. There was a simple conflict on 4.9 which
>>>>> also had to be resolved.
>>>>>
>>>>
>>>>
>>>> Thanks Sasha !
>>>
>>> Note, these had to all be dropped as they broke the build :(
>>>
>>> So can you please send us patches that at least build?  :)
>>>
>>
>> Do you have a build failure log ? I did build test it before sending it
>> over. I tried it again on 4.9, 4.14 and 4.19. I don't hit any build
>> failures here.
>>
>> Please could you share the log if you have it handy ?
> 
> It was in the stable -rc review emails, I don't have it handy, sorry.
> 

I think there is a bit of confusion here. If you're referring to

https://lkml.org/lkml/2020/1/11/634

as the build failure report, this is precisely my series fixes.
I sent this series to address the build break reported by Nathan.
The original patches were picked up from the "Fixes" tag automatically
which broke the build due to missing "event" parameter. This series
fixes those build issues and for sure builds fine for the affected
versions. Trust me ;-)

Cheers
Suzuki



> greg k-h
>