On 23/06/22 11:31, Sebastian Andrzej Siewior wrote: > On 2022-06-20 12:15:20 [+0100], Valentin Schneider wrote: >> Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an NMI >> panic() doesn't work. The cause of that lies in the PREEMPT_RT definition >> of mutex_trylock(): >> > … > >> Fixes: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context") >> Signed-off-by: Valentin Schneider <vschneid@xxxxxxxxxx> > > Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > >> --- >> v1 -> v2 >> ++++++++ >> >> o Changed from Peterson-like synchronization to simpler atomic_cmpxchg >> (Petr) >> o Slightly reworded changelog >> o Added Fixes: tag. Technically should be up to since kexec can happen >> in an NMI, but that isn't such a clear target > > RT-wise it would be needed for each release. So git tells me the Fixes: commit dates from v4.2; from [1] and [2] I get that both current longterm stable and stable-rt trees go as far back as v4.9, so I'm guessing if that gets picked up for the stable trees then it should make its way into the stable -rt trees? [1]: https://wiki.linuxfoundation.org/realtime/preempt_rt_versions [2]: https://www.kernel.org/category/releases.html > There is also a mutex_unlock() in case an image is missing. This can go > via the scheduler if there is a waiter which does not look good with the > NMI in the picture. > > Sebastian