> On 18 Apr 2024, at 13:20, Mike Rapoport <rppt@xxxxxxxxxx> wrote: > > On Tue, Apr 16, 2024 at 12:36:08PM +0300, Nadav Amit wrote: >> >> >> >> I might be missing something, but it seems a bit racy. >> >> IIUC, module_finalize() calls alternatives_smp_module_add(). At this >> point, since you don’t hold the text_mutex, some might do text_poke(), >> e.g., by enabling/disabling static-key, and the update would be >> overwritten. No? > > Right :( > Even worse, for UP case alternatives_smp_unlock() will "patch" still empty > area. > > So I'm thinking about calling alternatives_smp_module_add() from an > additional callback after the execmem_update_copy(). > > Does it make sense to you? Going over the code again - I might have just been wrong: I confused the alternatives and the jump-label mechanisms (as they do share a lot of code and characteristics). The jump-labels are updated when prepare_coming_module() is called, which happens after post_relocation() [which means they would be updated using text_poke() “inefficiently” but should be safe]. The “alternatives” appear only to use text_poke() (in contrast for text_poke_early()) from very specific few flows, e.g., common_cpu_up() -> alternatives_enable_smp(). Are those flows pose a problem after boot? Anyhow, sorry for the noise.
