On Thu, Feb 27, 2025 at 07:08:56PM +0100, Valentin Schneider wrote: > On 13/02/25 21:00, Jinjie Ruan wrote: > > Currently, x86, Riscv, Loongarch use the generic entry. Convert arm64 > > to use the generic entry infrastructure from kernel/entry/*. > > The generic entry makes maintainers' work easier and codes > > more elegant. > > > > Switch arm64 to generic IRQ entry first, which removed duplicate 100+ > > LOC and make Lazy preemption on arm64 available by adding a > > _TIF_NEED_RESCHED_LAZY bit and enabling ARCH_HAS_PREEMPT_LAZY. > > Just a drive-by comment as I'm interested in lazy preemption for arm64; > this series doesn't actually enable lazy preemption, is that for a > follow-up with the rest of the generic entry stuff? > > From a quick glance, it looks like everything is in place for enabling it.
Sorry, there's been some fractured discussion on this on the linux-rt-users list: https://lore.kernel.org/linux-rt-users/20241216190451.1c619...@mordecai.tesarici.cz/ The TL;DR is that lazy preemption doesn't actually depend on generic entry, and we should be able to enable it on arm64 independently of this series. I'd posted a quick hack which Mike Galbraith cleaned up: https://lore.kernel.org/linux-rt-users/a198a7dd9076f97b89d8882bb249b3bf303564ef.ca...@gmx.de/ ... but that was never posted as a new thread to LAKML. Would you be happy to take charge and take that patch, test it, and post it here (or spin your own working version)? I was happy with the way it looks but hadn't had the time for testing and so on. I expect that we'll merge the generic entry code too, but having them separate is a bit easier for bisection and backporting where people want lazy preemption in downstream trees. Mark.
