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 --- tools/testing/selftests/splice/.gitignore | 3 + tools/testing/selftests/splice/Makefile | 5 + tools/testing/selftests/splice/config | 1 + .../selftests/splice/default_file_splice_read.c | 9 ++ .../selftests/splice/default_file_splice_read.sh | 8 ++ tools/testing/selftests/splice/settings | 1 + .../testing/selftests/splice/short_splice_read.sh | 133 +++++++++++++++++++++ tools/testing/selftests/splice/splice_read.c | 57 +++++++++ 8 files changed, 217 insertions(+) create mode 100644 tools/testing/selftests/splice/.gitignore create mode 100644 tools/testing/selftests/splice/Makefile create mode 100644 tools/testing/selftests/splice/config create mode 100644 tools/testing/selftests/splice/default_file_splice_read.c create mode 100755 tools/testing/selftests/splice/default_file_splice_read.sh create mode 100644 tools/testing/selftests/splice/settings create mode 100755 tools/testing/selftests/splice/short_splice_read.sh create mode 100644 tools/testing/selftests/splice/splice_read.c (limited to 'tools/testing/selftests/splice') diff --git a/tools/testing/selftests/splice/.gitignore b/tools/testing/selftests/splice/.gitignore new file mode 100644 index 000000000..be8266f5d --- /dev/null +++ b/tools/testing/selftests/splice/.gitignore @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0-only +default_file_splice_read +splice_read diff --git a/tools/testing/selftests/splice/Makefile b/tools/testing/selftests/splice/Makefile new file mode 100644 index 000000000..541cd826d --- /dev/null +++ b/tools/testing/selftests/splice/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +TEST_PROGS := default_file_splice_read.sh short_splice_read.sh +TEST_GEN_PROGS_EXTENDED := default_file_splice_read splice_read + +include ../lib.mk diff --git a/tools/testing/selftests/splice/config b/tools/testing/selftests/splice/config new file mode 100644 index 000000000..058c92836 --- /dev/null +++ b/tools/testing/selftests/splice/config @@ -0,0 +1 @@ +CONFIG_TEST_LKM=m diff --git a/tools/testing/selftests/splice/default_file_splice_read.c b/tools/testing/selftests/splice/default_file_splice_read.c new file mode 100644 index 000000000..a3c6e5672 --- /dev/null +++ b/tools/testing/selftests/splice/default_file_splice_read.c @@ -0,0 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include + +int main(int argc, char **argv) +{ + splice(0, 0, 1, 0, 1<<30, 0); + return 0; +} diff --git a/tools/testing/selftests/splice/default_file_splice_read.sh b/tools/testing/selftests/splice/default_file_splice_read.sh new file mode 100755 index 000000000..490db5a2e --- /dev/null +++ b/tools/testing/selftests/splice/default_file_splice_read.sh @@ -0,0 +1,8 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +n=`./default_file_splice_read &2 + echo "$title ..." >&2 + + set +e + "$@" + rc=$? + set -e + + case "$rc" in + 0) + echo "ok: $title succeeded" >&2 + ;; + 1) + echo "FAIL: $title should work" >&2 + ret=$(( ret + 1 )) + ;; + *) + echo "FAIL: something else went wrong" >&2 + ret=$(( ret + 1 )) + ;; + esac +} + +expect_failure() +{ + title="$1" + shift + + echo "" >&2 + echo "$title ..." >&2 + + set +e + "$@" + rc=$? + set -e + + case "$rc" in + 0) + echo "FAIL: $title unexpectedly worked" >&2 + ret=$(( ret + 1 )) + ;; + 1) + echo "ok: $title correctly failed" >&2 + ;; + *) + echo "FAIL: something else went wrong" >&2 + ret=$(( ret + 1 )) + ;; + esac +} + +do_splice() +{ + filename="$1" + bytes="$2" + expected="$3" + report="$4" + + out=$("$DIR"/splice_read "$filename" "$bytes" | cat) + if [ "$out" = "$expected" ] ; then + echo " matched $report" >&2 + return 0 + else + echo " no match: '$out' vs $report" >&2 + return 1 + fi +} + +test_splice() +{ + filename="$1" + + echo " checking $filename ..." >&2 + + full=$(cat "$filename") + rc=$? + if [ $rc -ne 0 ] ; then + return 2 + fi + + two=$(echo "$full" | grep -m1 . | cut -c-2) + + # Make sure full splice has the same contents as a standard read. + echo " splicing 4096 bytes ..." >&2 + if ! do_splice "$filename" 4096 "$full" "full read" ; then + return 1 + fi + + # Make sure a partial splice see the first two characters. + echo " splicing 2 bytes ..." >&2 + if ! do_splice "$filename" 2 "$two" "'$two'" ; then + return 1 + fi + + return 0 +} + +### /proc/$pid/ has no splice interface; these should all fail. +expect_failure "proc_single_open(), seq_read() splice" test_splice /proc/$$/limits +expect_failure "special open(), seq_read() splice" test_splice /proc/$$/comm + +### /proc/sys/ has a splice interface; these should all succeed. +expect_success "proc_handler: proc_dointvec_minmax() splice" test_splice /proc/sys/fs/nr_open +expect_success "proc_handler: proc_dostring() splice" test_splice /proc/sys/kernel/modprobe +expect_success "proc_handler: special read splice" test_splice /proc/sys/kernel/version + +### /sys/ has no splice interface; these should all fail. +if ! [ -d /sys/module/test_module/sections ] ; then + expect_success "test_module kernel module load" modprobe test_module +fi +expect_success "kernfs attr splice" test_splice /sys/module/test_module/coresize +expect_success "kernfs binattr splice" test_splice /sys/module/test_module/sections/.init.text + +exit $ret diff --git a/tools/testing/selftests/splice/splice_read.c b/tools/testing/selftests/splice/splice_read.c new file mode 100644 index 000000000..46dae6a25 --- /dev/null +++ b/tools/testing/selftests/splice/splice_read.c @@ -0,0 +1,57 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include + +int main(int argc, char *argv[]) +{ + int fd; + size_t size; + ssize_t spliced; + + if (argc < 2) { + fprintf(stderr, "Usage: %s INPUT [BYTES]\n", argv[0]); + return EXIT_FAILURE; + } + + fd = open(argv[1], O_RDONLY); + if (fd < 0) { + perror(argv[1]); + return EXIT_FAILURE; + } + + if (argc == 3) + size = atol(argv[2]); + else { + struct stat statbuf; + + if (fstat(fd, &statbuf) < 0) { + perror(argv[1]); + return EXIT_FAILURE; + } + + if (statbuf.st_size > INT_MAX) { + fprintf(stderr, "%s: Too big\n", argv[1]); + return EXIT_FAILURE; + } + + size = statbuf.st_size; + } + + /* splice(2) file to stdout. */ + spliced = splice(fd, NULL, STDOUT_FILENO, NULL, + size, SPLICE_F_MOVE); + if (spliced < 0) { + perror("splice"); + return EXIT_FAILURE; + } + + close(fd); + return EXIT_SUCCESS; +} -- cgit v1.3.1