selftests/bpf: Add tests for css_task iter combining with cgroup iter

This patch adds a test which demonstrates how css_task iter can be combined
with cgroup iter and it won't cause deadlock, though cgroup iter is not
sleepable.

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20231031050438.93297-3-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
index e02feb5fae97dd814775c0149893b4507cef2332..574d9a0cdc8e4a33c730bcb11a4136d60f718e86 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
@@ -4,6 +4,7 @@
 #include <test_progs.h>
 #include <bpf/libbpf.h>
 #include <bpf/btf.h>
+#include "iters_css_task.skel.h"
 #include "cgroup_iter.skel.h"
 #include "cgroup_helpers.h"
 
@@ -263,6 +264,35 @@ close_cgrp:
        close(cgrp_fd);
 }
 
+static void test_walk_self_only_css_task(void)
+{
+       struct iters_css_task *skel;
+       int err;
+
+       skel = iters_css_task__open();
+       if (!ASSERT_OK_PTR(skel, "skel_open"))
+               return;
+
+       bpf_program__set_autoload(skel->progs.cgroup_id_printer, true);
+
+       err = iters_css_task__load(skel);
+       if (!ASSERT_OK(err, "skel_load"))
+               goto cleanup;
+
+       err = join_cgroup(cg_path[CHILD2]);
+       if (!ASSERT_OK(err, "join_cgroup"))
+               goto cleanup;
+
+       skel->bss->target_pid = getpid();
+       snprintf(expected_output, sizeof(expected_output),
+               PROLOGUE "%8llu\n" EPILOGUE, cg_id[CHILD2]);
+       read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[CHILD2],
+               BPF_CGROUP_ITER_SELF_ONLY, "test_walk_self_only_css_task");
+       ASSERT_EQ(skel->bss->css_task_cnt, 1, "css_task_cnt");
+cleanup:
+       iters_css_task__destroy(skel);
+}
+
 void test_cgroup_iter(void)
 {
        struct cgroup_iter *skel = NULL;
@@ -293,6 +323,9 @@ void test_cgroup_iter(void)
                test_walk_self_only(skel);
        if (test__start_subtest("cgroup_iter__dead_self_only"))
                test_walk_dead_self_only(skel);
+       if (test__start_subtest("cgroup_iter__self_only_css_task"))
+               test_walk_self_only_css_task();
+
 out:
        cgroup_iter__destroy(skel);
        cleanup_cgroups();

diff --git a/tools/testing/selftests/bpf/progs/iters_css_task.c b/tools/testing/selftests/bpf/progs/iters_css_task.c
index 5089ce384a1c7afa593ef273eaed8b043770e24e..384ff806990fa799b10ef134fddee124f9c601df 100644 (file)
--- a/tools/testing/selftests/bpf/progs/iters_css_task.c
+++ b/tools/testing/selftests/bpf/progs/iters_css_task.c
@@ -10,6 +10,7 @@
 
 char _license[] SEC("license") = "GPL";
 
+struct cgroup *bpf_cgroup_acquire(struct cgroup *p) __ksym;
 struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
 void bpf_cgroup_release(struct cgroup *p) __ksym;
 
@@ -45,3 +46,46 @@ int BPF_PROG(iter_css_task_for_each, struct vm_area_struct *vma,
 
        return -EPERM;
 }
+
+static inline u64 cgroup_id(struct cgroup *cgrp)
+{
+       return cgrp->kn->id;
+}
+
+SEC("?iter/cgroup")
+int cgroup_id_printer(struct bpf_iter__cgroup *ctx)
+{
+       struct seq_file *seq = ctx->meta->seq;
+       struct cgroup *cgrp, *acquired;
+       struct cgroup_subsys_state *css;
+       struct task_struct *task;
+       u64 cgrp_id;
+
+       cgrp = ctx->cgroup;
+
+       /* epilogue */
+       if (cgrp == NULL) {
+               BPF_SEQ_PRINTF(seq, "epilogue\n");
+               return 0;
+       }
+
+       /* prologue */
+       if (ctx->meta->seq_num == 0)
+               BPF_SEQ_PRINTF(seq, "prologue\n");
+
+       cgrp_id = cgroup_id(cgrp);
+
+       BPF_SEQ_PRINTF(seq, "%8llu\n", cgrp_id);
+
+       acquired = bpf_cgroup_from_id(cgrp_id);
+       if (!acquired)
+               return 0;
+       css = &acquired->self;
+       css_task_cnt = 0;
+       bpf_for_each(css_task, task, css, CSS_TASK_ITER_PROCS) {
+               if (task->pid == target_pid)
+                       css_task_cnt++;
+       }
+       bpf_cgroup_release(acquired);
+       return 0;
+}