On Fri, Apr 21 2023 at 14:45, Greg KH wrote:
> On Fri, Apr 21, 2023 at 09:29:08AM +0200, Thomas Gleixner wrote:
>> On Wed, Apr 19 2023 at 09:25, Sebastian Andrzej Siewior wrote:
>> > On 2023-04-18 18:25:48 [+0200], Greg KH wrote:
>> >> > Could this be please backported to 5.15 and earlier? It is already part
>> >> > of the 6.X kernels. I asked about this by the end of January and I'm
>> >> > kindly asking again ;)
>> >>
>> >> I thought this was only an issues when using the out-of-tree RT patches
>> >> with these kernels, right? Or is it relevant for 5.15.y from kernel.org
>> >> without anything else?
>> >
>> > The out-of-tree RT patches make extensive use of the code. Since it is
>> > upstream code, I assumed it should go via the official stable trees.
>> > Without RT, the code is limited the rt_mutex_lock() used by I2C and the
>> > RCU booster-mutex.
>>
>> Which is a reason to route it through the upstream stable trees, no?
>
> I do not understand. Why would we take a patch in the stable tree
> because an out-of-tree change requires it?
The change is to the rtmutex core which _IS_ used in tree by futex, RCU
and some drivers.
Just because the problem was observed on RT it does not make the
mainline usage of RTMUTEXes magically unaffected. The missing acquire
semantics are required there too.
Thanks,
tglx
