On Thu, Sep 18, 2025 at 03:10:18PM -0400, Steven Rostedt wrote: > On Thu, 18 Sep 2025 19:32:20 +0200 > Peter Zijlstra <[email protected]> wrote: > > > > Now, task_work_run() is in the exit_to_user_mode_loop() which is notably > > > *before* exit_to_user_mode() which does the unwind_reset_info(). > > > > > > What happens if we get an NMI requesting an unwind after > > > unwind_reset_info() while still very much being in the kernel on the way > > > out? > > > > AFAICT it will try and do a task_work_add(TWA_RESUME) from NMI context, > > and this will fail horribly. > > > > If you do something like: > > > > twa_mode = in_nmi() ? TWA_NMI_CURRENT : TWA_RESUME; > > task_work_add(foo, twa_mode); > > > > it might actually work. > > Ah, the comment for TWA_RESUME didn't express this restriction. > > That does look like that would work as the way I expected task_work to > handle this case.
BTW, I remember Peter had a fix for TWA_NMI_CURRENT, I guess it got lost in the shuffle or did something else happen in the meantime? https://lore.kernel.org/[email protected] -- Josh
