On Tue 2022-05-17 11:48:31, Jason A. Donenfeld wrote: > Hi Petr, > > On Tue, May 17, 2022 at 11:04:54AM +0200, Petr Mladek wrote: > > I would go even further. The workqueue is needed only because we are not > > able to switch the static branch in an atomic context. > > > > But the static branch looks like an over-optimization. > > vsprintf() is a slow path. It will be enough to use a normal > > variable. > > > > Well, it would be nice to check it without the spinlock to keep it > > fast and avoid problems with the spin lock during panic(). > > > > What about? > > That all makes sense to me, but I'm a bit worried about changing too > much from the original design in a commit mostly intended on removing > things from random.c. Maybe we can do the patch I sent here, and then > once that lands in 5.19, we can do some more simplifications as > standalone commits that you can assess. Or if you're adamant about doing > this now, maybe you can send a patch that I can apply on _top_ of this > commit here? > > The reason I'm a bit cautious is because I recall the original code from > Tobin way back had some smp_wmb() just like this, but it got removed and > replaced with that static branch. So at least somebody felt differently > about it. Which means it'll probably be a whole discussion with more > people, and I'm probably not the right person to lead that. Fair enough. > > Well, your approach with static_key is fine as well. Feel free > > to use: > > > > Acked-by: Petr Mladek <pmladek@xxxxxxxx> > > Okay, I'll do this. And then let's circle around the memory barriers > whenever you feel like it later. OK, let's stick with your version in 5.19. I will later send a patch with the barriers when time permits. But it will probably be for the next release. Best Regards, Petr
