On Thu, Sep 06, 2018 at 07:42:14PM +0000, Nadav Amit wrote: > at 12:40 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > On Sun, Sep 02, 2018 at 10:32:19AM -0700, Nadav Amit wrote: > >> text_mutex is expected to be held before text_poke() is called, but we > >> cannot add a lockdep assertion since kgdb does not take it, and instead > >> *supposedly* ensures the lock is not taken and will not be acquired by > >> any other core while text_poke() is running. > >> > >> The reason for the "supposedly" comment is that it is not entirely clear > >> that this would be the case if gdb_do_roundup is zero. > > > > Argh, that's pretty shit code... > > > > Not only is that text_mutex abuse ugly, so too is the fixmap usage from > > IRQ context. I suppose this really does require your alternative mm > > patches for text_poke(). > > Right, I forgot about that… With that CR3 trickery, we can rid ourselves of the text_mutex requirement, since concurrent text_poke is 'safe'. That would clean up the kgdb code quite a bit.
