From a9e3760b0838299649c0d57cca44daaf40ba3c33 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Sep 2026 22:12:34 -1000 Subject: sched_ext: Maintain an online cid mask in the scheduler arena Schedulers on the default cid mapping treat [0, nr_online_cids) as the online set and restart on hotplug. Schedulers that install their own mapping with scx_bpf_cid_override() have no way to learn which cids are online: the count no longer identifies members and the CPU-form cpumask is unusable from cid programs. This is an obvious hole in the cid API. Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's arena, allocated alongside the per-CPU scratch masks and populated after the cid mapping is finalized and before ops.init(), for child schedulers too. The pointer stays valid through ops.exit() with no reference to take. It is the arena offset as a void pointer, the same form struct_ops arena arguments arrive in. The verifier types the void return as a scalar for the program's arena cast. The mask follows the SCX hotplug notifications: seeded from cpu_active_mask and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask only inside a hotplug transition. Updates walk the scheduler list under the lock that also serializes unlinking. Reads are live, not atomic snapshots. Root initialization excludes hotplug. v2: Reworded the getter kerneldoc (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- scripts/Kconfig.include | 78 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 78 insertions(+) create mode 100644 scripts/Kconfig.include (limited to 'scripts/Kconfig.include') diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include new file mode 100644 index 000000000..fc10671c2 --- /dev/null +++ b/scripts/Kconfig.include @@ -0,0 +1,78 @@ +# SPDX-License-Identifier: GPL-2.0-only +# Kconfig helper macros + +# Convenient variables +comma := , +quote := " +squote := ' +empty := +space := $(empty) $(empty) +dollar := $ +right_paren := ) +left_paren := ( + +# $(if-success,,,) +# Return if exits with 0, otherwise. +if-success = $(shell,{ $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)") + +# $(success,) +# Return y if exits with 0, n otherwise +success = $(if-success,$(1),y,n) + +# $(failure,) +# Return n if exits with 0, y otherwise +failure = $(if-success,$(1),n,y) + +# $(cc-option,) +# Return y if the compiler supports , n otherwise +cc-option = $(success,trap "rm -rf .tmp_$$" EXIT; mkdir .tmp_$$; $(CC) -Werror $(CLANG_FLAGS) $(1) -c -x c /dev/null -o .tmp_$$/tmp.o) + +# $(ld-option,) +# Return y if the linker supports , n otherwise +ld-option = $(success,$(LD) -v $(1)) + +# $(as-instr,) +# Return y if the assembler supports , n otherwise +as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) $(2) -Wa$(comma)--fatal-warnings -c -x assembler-with-cpp -o /dev/null -) +as-instr64 = $(as-instr,$(1),$(m64-flag)) + +# check if $(CC) and $(LD) exist +$(error-if,$(failure,command -v $(CC)),C compiler '$(CC)' not found) +$(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found) + +# Get the C compiler name, version, and error out if it is not supported. +cc-info := $(shell,$(srctree)/scripts/cc-version.sh $(CC)) +$(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this C compiler is not supported.) +cc-name := $(shell,set -- $(cc-info) && echo $1) +cc-version := $(shell,set -- $(cc-info) && echo $2) + +# Get the assembler name, version, and error out if it is not supported. +as-info := $(shell,$(srctree)/scripts/as-version.sh $(CC) $(CLANG_FLAGS)) +$(error-if,$(success,test -z "$(as-info)"),Sorry$(comma) this assembler is not supported.) +as-name := $(shell,set -- $(as-info) && echo $1) +as-version := $(shell,set -- $(as-info) && echo $2) + +# Get the linker name, version, and error out if it is not supported. +ld-info := $(shell,$(srctree)/scripts/ld-version.sh $(LD)) +$(error-if,$(success,test -z "$(ld-info)"),Sorry$(comma) this linker is not supported.) +ld-name := $(shell,set -- $(ld-info) && echo $1) +ld-version := $(shell,set -- $(ld-info) && echo $2) + +# machine bit flags +# $(m32-flag): -m32 if the compiler supports it, or an empty string otherwise. +# $(m64-flag): -m64 if the compiler supports it, or an empty string otherwise. +cc-option-bit = $(if-success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null,$(1)) +m32-flag := $(cc-option-bit,-m32) +m64-flag := $(cc-option-bit,-m64) + +# Test whether the compiler can link userspace applications +cc_can_link_user = $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(1)) + +rustc-version := $(shell,$(srctree)/scripts/rustc-version.sh $(RUSTC)) +rustc-llvm-version := $(shell,$(srctree)/scripts/rustc-llvm-version.sh $(RUSTC)) + +# $(rustc-option,) +# Return y if the Rust compiler supports , n otherwise +# If you are testing for unstable features, consider testing RUSTC_VERSION +# instead, as features may have different completeness while available. +rustc-option = $(success,trap "rm -rf .tmp_$$" EXIT; mkdir .tmp_$$; $(RUSTC) $(1) --crate-type=rlib /dev/null --out-dir=.tmp_$$ -o .tmp_$$/tmp.rlib) -- cgit v1.3.1