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Date:   Sat, 2 Jul 2022 01:06:03 +1000
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Subject: Re: [PATCH v7 2/4] kernfs: Change kernfs_notify_list to llist.
Content-Language: en-US
To:     Marek Szyprowski <m.szyprowski@samsung.com>, tj@kernel.org,
        gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk
Cc:     linux-kernel@vger.kernel.org
References: <20220615021059.862643-1-imran.f.khan@oracle.com>
 <20220615021059.862643-3-imran.f.khan@oracle.com>
 <CGME20220701112210eucas1p2d2db45881086f41b73527f7536537aa5@eucas1p2.samsung.com>
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From:   Imran Khan <imran.f.khan@oracle.com>
In-Reply-To: <ad06d3c3-7878-9106-e118-f89e2de91a1f@samsung.com>
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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@zeniv.linux.org.uk>
>>>> Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
>>>> Acked-by: Tejun Heo <tj@kernel.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@samsung.com>
> 
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.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/