Steven and Paul recently discussed some issues when using RCU functionality in ftrace handlers. A good summary can be found at https://lkml.kernel.org/r/20170412115304.3077d...@gandalf.local.home
This discussion made us to revisit the ftrace handler used by the livepatches. Some changes seem to be needed. A perfect solution looks rather complicated. I have implemented a sub-optimal one and split it into three patches for easier review. Please, note that we were on the safe side before introducing the hybrid consistency model. The ftrace handler worked correctly with empty function stack. Also the patch removal was not possible. But we need to be more careful now. Petr Mladek (3): livepatch/rcu: Guarantee consistency when patching idle kthreads livepatch/rcu: Warn when system consistency is broken in RCU code livepatch/rcu: Disable livepatch removal when safety is not guaranteed Documentation/livepatch/livepatch.txt | 19 +++++++++++++++++++ kernel/livepatch/patch.c | 14 ++++++++++++++ kernel/livepatch/transition.c | 7 ++++++- kernel/livepatch/transition.h | 2 ++ 4 files changed, 41 insertions(+), 1 deletion(-) -- 1.8.5.6
