linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Thorsten Leemhuis <regressions@leemhuis.info>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will@kernel.org>,
	Amit Pundir <amit.pundir@linaro.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Sibi Sankar <quic_sibis@quicinc.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	Robin Murphy <robin.murphy@arm.com>,
	andersson@kernel.org, sumit.semwal@linaro.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, hch@lst.de
Subject: Re: [PATCH] Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()"
Date: Fri, 2 Dec 2022 17:27:24 +0100	[thread overview]
Message-ID: <395ad6ef-eb54-ec7e-e131-714f23c84d7a@leemhuis.info> (raw)
In-Reply-To: <Y4ojXyXMX2p+RVBR@kroah.com>



On 02.12.22 17:10, Greg KH wrote:
> On Fri, Dec 02, 2022 at 11:34:30AM +0100, Thorsten Leemhuis wrote:
>> On 02.12.22 11:03, Will Deacon wrote:
>>> On Fri, Dec 02, 2022 at 09:54:05AM +0100, Thorsten Leemhuis wrote:
>>>> On 02.12.22 09:26, Amit Pundir wrote:
>>>>> On Thu, 1 Dec 2022 at 23:15, Catalin Marinas <catalin.marinas@arm.com> wrote:
>>>>>>
>>>>>> On Thu, Dec 01, 2022 at 10:29:39AM +0100, Thorsten Leemhuis wrote:
>>>>>>> Has any progress been made to fix this regression? It afaics is not a
>>>>>>> release critical issue, but well, it still would be nice to get this
>>>>>>> fixed before 6.1 is released.
>>>>>>
>>>>>> The only (nearly) risk-free "fix" for 6.1 would be to revert the commit
>>>>>> that exposed the driver bug. It doesn't fix the actual bug, it only
>>>>>> makes it less likely to happen.
>>>>>>
>>>>>> I like the original commit removing the cache invalidation as it shows
>>>>>> drivers not behaving properly
>>>>
>>>> Yeah, I understand that, but I guess it's my job to ask at this point:
>>>> "is continuing to live with the old behavior for one or two more cycles"
>>>> that much of a problem"?
>>>
>>> That wouldn't be a problem. The problem is that I haven't see any efforts
>>> from the Qualcomm side to actually fix the drivers [...]
>>
>> Thx for sharing the details. I can fully understand your pain. But well,
>> in the end it looks to me like this commit it intentionally breaking
>> something that used to work -- which to my understanding of the "no
>> regression rule" is not okay, even if things only worked by chance and
>> not flawless.
> 
> "no regressions" for userspace code, this is broken, out-of-tree driver
> code, right?

If so: apologies. But that's not the impression I got, as Amit wrote "I
can reproduce this crash on vanilla v6.1-rc1 as well with no out-of-tree
drivers." here:
https://lore.kernel.org/linux-arm-kernel/CAMi1Hd3H2k1J8hJ6e-Miy5+nVDNzv6qQ3nN-9929B0GbHJkXEg@mail.gmail.com/

>  I do not think any in-kernel drivers have this issue today
> from what I can tell, but if I am wrong here, please let me know.
> 
> We don't keep stable apis, or even functionality, for out-of-tree kernel
> code as that would be impossible for us to do for obvious reasons.

Ciao, Thorsten

  reply	other threads:[~2022-12-02 16:27 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-14 11:03 [PATCH] Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()" Manivannan Sadhasivam
2022-11-14 11:29 ` Manivannan Sadhasivam
2022-11-14 14:11 ` Will Deacon
2022-11-14 15:14   ` Robin Murphy
2022-11-14 17:38     ` Catalin Marinas
2022-11-18 10:54       ` Manivannan Sadhasivam
2022-11-18 12:33         ` Will Deacon
2022-11-21  6:42           ` Manivannan Sadhasivam
2022-11-21 10:12             ` Sibi Sankar
2022-11-24 11:55               ` Catalin Marinas
2022-12-01  9:29                 ` Thorsten Leemhuis
2022-12-01 17:45                   ` Catalin Marinas
2022-12-02  8:26                     ` Amit Pundir
2022-12-02  8:54                       ` Thorsten Leemhuis
2022-12-02 10:03                         ` Will Deacon
2022-12-02 10:34                           ` Thorsten Leemhuis
2022-12-02 16:10                             ` Greg KH
2022-12-02 16:27                               ` Thorsten Leemhuis [this message]
2022-12-02 16:32                                 ` Greg KH
2022-12-02 17:14                                   ` Manivannan Sadhasivam
2022-12-05 14:24                                     ` Will Deacon
2022-12-06  9:21                                       ` Manivannan Sadhasivam
2022-12-06  9:58                                         ` Will Deacon
2022-12-02 10:54                           ` Manivannan Sadhasivam
2022-11-28  5:44 ` Thorsten Leemhuis
2022-11-28  8:15   ` Manivannan Sadhasivam
2022-12-08  4:59 ` Leonard Lausen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=395ad6ef-eb54-ec7e-e131-714f23c84d7a@leemhuis.info \
    --to=regressions@leemhuis.info \
    --cc=amit.pundir@linaro.org \
    --cc=andersson@kernel.org \
    --cc=catalin.marinas@arm.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=hch@lst.de \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=manivannan.sadhasivam@linaro.org \
    --cc=quic_sibis@quicinc.com \
    --cc=robin.murphy@arm.com \
    --cc=sumit.semwal@linaro.org \
    --cc=will@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).