On Tue, Nov 07, 2023 at 01:56:46PM -0800, Ankur Arora wrote: > What's broken: > - ARCH_NO_PREEMPT (See patch-45 "preempt: ARCH_NO_PREEMPT only preempts > lazily") > - Non-x86 architectures. It's trivial to support other archs (only need > to add TIF_NEED_RESCHED_LAZY) but wanted to hold off until I got some > comments on the series. > (From some testing on arm64, didn't find any surprises.) When you say "testing on arm64, didn't find any surprises", I assume you mean with an additional patch adding TIF_NEED_RESCHED_LAZY? Applying this series as-is atop v6.6-rc7 and building defconfig (with GCC 13.2.0) blows up with: | In file included from ./arch/arm64/include/asm/preempt.h:5, | from ./include/linux/preempt.h:79, | from ./include/linux/spinlock.h:56, | from ./include/linux/mmzone.h:8, | from ./include/linux/gfp.h:7, | from ./include/linux/slab.h:16, | from ./include/linux/resource_ext.h:11, | from ./include/linux/acpi.h:13, | from ./include/acpi/apei.h:9, | from ./include/acpi/ghes.h:5, | from ./include/linux/arm_sdei.h:8, | from arch/arm64/kernel/asm-offsets.c:10: | ./include/linux/thread_info.h:63:2: error: #error "Arch needs to define TIF_NEED_RESCHED_LAZY" | 63 | #error "Arch needs to define TIF_NEED_RESCHED_LAZY" | | ^~~~~ | ./include/linux/thread_info.h:66:42: error: 'TIF_NEED_RESCHED_LAZY' undeclared here (not in a function); did you mean 'TIF_NEED_RESCHED'? | 66 | #define TIF_NEED_RESCHED_LAZY_OFFSET (TIF_NEED_RESCHED_LAZY - TIF_NEED_RESCHED) | | ^~~~~~~~~~~~~~~~~~~~~ | ./include/linux/thread_info.h:70:24: note: in expansion of macro 'TIF_NEED_RESCHED_LAZY_OFFSET' | 70 | RESCHED_lazy = TIF_NEED_RESCHED_LAZY_OFFSET, | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ | make[2]: *** [scripts/Makefile.build:116: arch/arm64/kernel/asm-offsets.s] Error 1 | make[1]: *** [/home/mark/src/linux/Makefile:1202: prepare0] Error 2 | make: *** [Makefile:234: __sub-make] Error 2 Note that since arm64 doesn't use the generic entry code, that also requires changes to arm64_preempt_schedule_irq() in arch/arm64/kernel/entry-common.c, to handle TIF_NEED_RESCHED_LAZY. > - ftrace support for need-resched-lazy is incomplete What exactly do we need for ftrace here? Thanks, Mark.
