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/perf/tests/fdarray.c | 163 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 163 insertions(+) create mode 100644 tools/perf/tests/fdarray.c (limited to 'tools/perf/tests/fdarray.c') diff --git a/tools/perf/tests/fdarray.c b/tools/perf/tests/fdarray.c new file mode 100644 index 000000000..40983c357 --- /dev/null +++ b/tools/perf/tests/fdarray.c @@ -0,0 +1,163 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include "util/debug.h" +#include "tests/tests.h" + +static void fdarray__init_revents(struct fdarray *fda, short revents) +{ + int fd; + + fda->nr = fda->nr_alloc; + + for (fd = 0; fd < fda->nr; ++fd) { + fda->entries[fd].fd = fda->nr - fd; + fda->entries[fd].events = revents; + fda->entries[fd].revents = revents; + } +} + +static int fdarray__fprintf_prefix(struct fdarray *fda, const char *prefix, FILE *fp) +{ + int printed = 0; + + if (verbose <= 0) + return 0; + + printed += fprintf(fp, "\n%s: ", prefix); + return printed + fdarray__fprintf(fda, fp); +} + +static int test__fdarray__filter(struct test_suite *test __maybe_unused, int subtest __maybe_unused) +{ + int nr_fds, err = TEST_FAIL; + struct fdarray *fda = fdarray__new(5, 5); + + if (fda == NULL) { + pr_debug("\nfdarray__new() failed!"); + goto out; + } + + fdarray__init_revents(fda, POLLIN); + nr_fds = fdarray__filter(fda, POLLHUP, NULL, NULL); + if (nr_fds != fda->nr_alloc) { + pr_debug("\nfdarray__filter()=%d != %d shouldn't have filtered anything", + nr_fds, fda->nr_alloc); + goto out_delete; + } + + fdarray__init_revents(fda, POLLHUP); + nr_fds = fdarray__filter(fda, POLLHUP, NULL, NULL); + if (nr_fds != 0) { + pr_debug("\nfdarray__filter()=%d != %d, should have filtered all fds", + nr_fds, fda->nr_alloc); + goto out_delete; + } + + fdarray__init_revents(fda, POLLHUP); + fda->entries[2].revents = POLLIN; + + pr_debug("\nfiltering all but fda->entries[2]:"); + fdarray__fprintf_prefix(fda, "before", stderr); + nr_fds = fdarray__filter(fda, POLLHUP, NULL, NULL); + fdarray__fprintf_prefix(fda, " after", stderr); + if (nr_fds != 1) { + pr_debug("\nfdarray__filter()=%d != 1, should have left just one event", nr_fds); + goto out_delete; + } + + fdarray__init_revents(fda, POLLHUP); + fda->entries[0].revents = POLLIN; + fda->entries[3].revents = POLLIN; + + pr_debug("\nfiltering all but (fda->entries[0], fda->entries[3]):"); + fdarray__fprintf_prefix(fda, "before", stderr); + nr_fds = fdarray__filter(fda, POLLHUP, NULL, NULL); + fdarray__fprintf_prefix(fda, " after", stderr); + if (nr_fds != 2) { + pr_debug("\nfdarray__filter()=%d != 2, should have left just two events", + nr_fds); + goto out_delete; + } + + pr_debug("\n"); + + err = 0; +out_delete: + fdarray__delete(fda); +out: + return err; +} + +static int test__fdarray__add(struct test_suite *test __maybe_unused, int subtest __maybe_unused) +{ + int err = TEST_FAIL; + struct fdarray *fda = fdarray__new(2, 2); + + if (fda == NULL) { + pr_debug("\nfdarray__new() failed!"); + goto out; + } + +#define FDA_CHECK(_idx, _fd, _revents) \ + if (fda->entries[_idx].fd != _fd) { \ + pr_debug("\n%d: fda->entries[%d](%d) != %d!", \ + __LINE__, _idx, fda->entries[1].fd, _fd); \ + goto out_delete; \ + } \ + if (fda->entries[_idx].events != (_revents)) { \ + pr_debug("\n%d: fda->entries[%d].revents(%d) != %d!", \ + __LINE__, _idx, fda->entries[_idx].fd, _revents); \ + goto out_delete; \ + } + +#define FDA_ADD(_idx, _fd, _revents, _nr) \ + if (fdarray__add(fda, _fd, _revents, fdarray_flag__default) < 0) { \ + pr_debug("\n%d: fdarray__add(fda, %d, %d) failed!", \ + __LINE__,_fd, _revents); \ + goto out_delete; \ + } \ + if (fda->nr != _nr) { \ + pr_debug("\n%d: fdarray__add(fda, %d, %d)=%d != %d", \ + __LINE__,_fd, _revents, fda->nr, _nr); \ + goto out_delete; \ + } \ + FDA_CHECK(_idx, _fd, _revents) + + FDA_ADD(0, 1, POLLIN, 1); + FDA_ADD(1, 2, POLLERR, 2); + + fdarray__fprintf_prefix(fda, "before growing array", stderr); + + FDA_ADD(2, 35, POLLHUP, 3); + + if (fda->entries == NULL) { + pr_debug("\nfdarray__add(fda, 35, POLLHUP) should have allocated fda->pollfd!"); + goto out_delete; + } + + fdarray__fprintf_prefix(fda, "after 3rd add", stderr); + + FDA_ADD(3, 88, POLLIN | POLLOUT, 4); + + fdarray__fprintf_prefix(fda, "after 4th add", stderr); + + FDA_CHECK(0, 1, POLLIN); + FDA_CHECK(1, 2, POLLERR); + FDA_CHECK(2, 35, POLLHUP); + FDA_CHECK(3, 88, POLLIN | POLLOUT); + +#undef FDA_ADD +#undef FDA_CHECK + + pr_debug("\n"); + + err = 0; +out_delete: + fdarray__delete(fda); +out: + return err; +} + +DEFINE_SUITE("Filter fds with revents mask in a fdarray", fdarray__filter); +DEFINE_SUITE("Add fd to a fdarray, making it autogrow", fdarray__add); -- cgit v1.3.1