linux-kernel - Re: [PATCH v7 2/4] kernfs: Change kernfs_notify

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Message-ID: <ab856471-99f5-b70a-cf4e-5293a7d52957@oracle.com>
Date:   Sat, 2 Jul 2022 01:06:03 +1000
From:   Imran Khan <imran.f.khan@...cle.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>, tj@...nel.org,
        gregkh@...uxfoundation.org, viro@...iv.linux.org.uk
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/4] kernfs: Change kernfs_notify_list to llist.

Hello,

On 1/7/22 10:49 pm, Marek Szyprowski wrote:
> Hi,
> 
> On 01.07.2022 14:20, Imran Khan wrote:
>> On 1/7/22 9:22 pm, Marek Szyprowski wrote:
>>> On 15.06.2022 04:10, Imran Khan wrote:
>>>> At present kernfs_notify_list is implemented as a singly linked
>>>> list of kernfs_node(s), where last element points to itself and
>>>> value of ->attr.next tells if node is present on the list or not.
>>>> Both addition and deletion to list happen under kernfs_notify_lock.
>>>>
>>>> Change kernfs_notify_list to llist so that addition to list can heppen
>>>> locklessly.
>>>>
>>>> Suggested by: Al Viro <viro@...iv.linux.org.uk>
>>>> Signed-off-by: Imran Khan <imran.f.khan@...cle.com>
>>>> Acked-by: Tejun Heo <tj@...nel.org>
>>> This patch landed in linux next-20220630 as commit b8f35fa1188b
>>> ("kernfs: Change kernfs_notify_list to llist."). Unfortunately, it
>>> causes serious regression on my test systems. It can be easily noticed
>>> in the logs by the following warning:
>>>
[...]
> 
> Yes, this fixes the issue. Feel free to add:
> 
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> 
> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> 

Thanks a lot for testing. Sure I have added these tags. I have
send the patch for review at [1].

> Maybe it is related to the fact, that I have earlycon enabled on those 
> machines?
> 
For sure it is occuring with some tweaking in console settings. So far both the
reported occurences have this thing in common. I will be able to confirm further
if I could reproduce this locally and I am trying that at the moment.
I will share when I have some more findings.


Thanks
-- Imran

[1]: https://lore.kernel.org/lkml/20220701145047.2206900-1-imran.f.khan@oracle.com/