On 2023-04-21 17:30:24 [+0200], Thomas Gleixner wrote: > >> > 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. not back stab but to clarify: futex does not use the annotation (it does not use the fastpath) but RCU-boosting _and_ I2C-bus code does use it. So both mainline users users of the rtmutex code are affected. > 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 Sebastian
