From 2669dde7a8c67e3efe8052d75d6040de2cbb5e5a Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Wed, 11 Feb 2026 10:57:47 -0800 Subject: [PATCH] selftests/bpf: Fix map_kptr grace period wait Commit c27cea4416a3 ("rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast") broke map_kptr selftest since it removed the function we were kprobing. Use a new kfunc that invokes call_rcu_tasks_trace and sets a program provided pointer to an integer to 1. Technically this can be unsafe if the memory being written to from the callback disappears, but this is just for usage in a test where we ensure we spin until we see the value to be set to 1, so it's ok. Reported-by: Shung-Hsi Yu Fixes: c27cea4416a3 ("rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast") Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260211185747.3630539-1-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- .../selftests/bpf/prog_tests/map_kptr.c | 15 ++++------ .../selftests/bpf/progs/rcu_tasks_trace_gp.c | 30 +++---------------- .../selftests/bpf/test_kmods/bpf_testmod.c | 28 +++++++++++++++++ .../bpf/test_kmods/bpf_testmod_kfunc.h | 1 + 4 files changed, 39 insertions(+), 35 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/map_kptr.c b/tools/testing/selftests/bpf/prog_tests/map_kptr.c index f372162c0280..03b46f17cf53 100644 --- a/tools/testing/selftests/bpf/prog_tests/map_kptr.c +++ b/tools/testing/selftests/bpf/prog_tests/map_kptr.c @@ -118,15 +118,16 @@ exit: static int kern_sync_rcu_tasks_trace(struct rcu_tasks_trace_gp *rcu) { - long gp_seq = READ_ONCE(rcu->bss->gp_seq); LIBBPF_OPTS(bpf_test_run_opts, opts); + int ret; - if (!ASSERT_OK(bpf_prog_test_run_opts(bpf_program__fd(rcu->progs.do_call_rcu_tasks_trace), - &opts), "do_call_rcu_tasks_trace")) + WRITE_ONCE(rcu->bss->done, 0); + ret = bpf_prog_test_run_opts(bpf_program__fd(rcu->progs.call_rcu_tasks_trace), &opts); + if (!ASSERT_OK(ret, "call_rcu_tasks_trace")) return -EFAULT; - if (!ASSERT_OK(opts.retval, "opts.retval == 0")) + if (!ASSERT_OK(opts.retval, "call_rcu_tasks_trace retval")) return -EFAULT; - while (gp_seq == READ_ONCE(rcu->bss->gp_seq)) + while (!READ_ONCE(rcu->bss->done)) sched_yield(); return 0; } @@ -159,8 +160,6 @@ void serial_test_map_kptr(void) skel = rcu_tasks_trace_gp__open_and_load(); if (!ASSERT_OK_PTR(skel, "rcu_tasks_trace_gp__open_and_load")) return; - if (!ASSERT_OK(rcu_tasks_trace_gp__attach(skel), "rcu_tasks_trace_gp__attach")) - goto end; if (test__start_subtest("success-map")) { test_map_kptr_success(true); @@ -180,7 +179,5 @@ void serial_test_map_kptr(void) test_map_kptr_success(true); } -end: rcu_tasks_trace_gp__destroy(skel); - return; } diff --git a/tools/testing/selftests/bpf/progs/rcu_tasks_trace_gp.c b/tools/testing/selftests/bpf/progs/rcu_tasks_trace_gp.c index df4873558634..189c05c6abcc 100644 --- a/tools/testing/selftests/bpf/progs/rcu_tasks_trace_gp.c +++ b/tools/testing/selftests/bpf/progs/rcu_tasks_trace_gp.c @@ -1,36 +1,14 @@ // SPDX-License-Identifier: GPL-2.0 #include -#include #include +#include "../test_kmods/bpf_testmod_kfunc.h" -struct task_ls_map { - __uint(type, BPF_MAP_TYPE_TASK_STORAGE); - __uint(map_flags, BPF_F_NO_PREALLOC); - __type(key, int); - __type(value, int); -} task_ls_map SEC(".maps"); - -long gp_seq; +int done; SEC("syscall") -int do_call_rcu_tasks_trace(void *ctx) -{ - struct task_struct *current; - int *v; - - current = bpf_get_current_task_btf(); - v = bpf_task_storage_get(&task_ls_map, current, NULL, BPF_LOCAL_STORAGE_GET_F_CREATE); - if (!v) - return 1; - /* Invoke call_rcu_tasks_trace */ - return bpf_task_storage_delete(&task_ls_map, current); -} - -SEC("kprobe/rcu_tasks_trace_postgp") -int rcu_tasks_trace_postgp(void *ctx) +int call_rcu_tasks_trace(void *ctx) { - __sync_add_and_fetch(&gp_seq, 1); - return 0; + return bpf_kfunc_call_test_call_rcu_tasks_trace(&done); } char _license[] SEC("license") = "GPL"; diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c index 186a25ab429a..e62c6b78657f 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include #include "bpf_testmod.h" @@ -885,6 +886,32 @@ __bpf_kfunc void bpf_kfunc_call_test_sleepable(void) { } +struct bpf_kfunc_rcu_tasks_trace_data { + struct rcu_head rcu; + int *done; +}; + +static void bpf_kfunc_rcu_tasks_trace_cb(struct rcu_head *rhp) +{ + struct bpf_kfunc_rcu_tasks_trace_data *data; + + data = container_of(rhp, struct bpf_kfunc_rcu_tasks_trace_data, rcu); + WRITE_ONCE(*data->done, 1); + kfree(data); +} + +__bpf_kfunc int bpf_kfunc_call_test_call_rcu_tasks_trace(int *done) +{ + struct bpf_kfunc_rcu_tasks_trace_data *data; + + data = kmalloc(sizeof(*data), GFP_ATOMIC); + if (!data) + return -ENOMEM; + data->done = done; + call_rcu_tasks_trace(&data->rcu, bpf_kfunc_rcu_tasks_trace_cb); + return 0; +} + __bpf_kfunc int bpf_kfunc_init_sock(struct init_sock_args *args) { int proto; @@ -1222,6 +1249,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test_destructive, KF_DESTRUCTIVE) BTF_ID_FLAGS(func, bpf_kfunc_call_test_static_unused_arg) BTF_ID_FLAGS(func, bpf_kfunc_call_test_offset) BTF_ID_FLAGS(func, bpf_kfunc_call_test_sleepable, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_kfunc_call_test_call_rcu_tasks_trace) BTF_ID_FLAGS(func, bpf_kfunc_init_sock, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_kfunc_close_sock, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_kfunc_call_kernel_connect, KF_SLEEPABLE) diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h index d5c5454e257e..b393bf771131 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h @@ -118,6 +118,7 @@ void bpf_kfunc_call_test_mem_len_fail2(__u64 *mem, int len) __ksym; void bpf_kfunc_call_test_destructive(void) __ksym; void bpf_kfunc_call_test_sleepable(void) __ksym; +int bpf_kfunc_call_test_call_rcu_tasks_trace(int *done) __ksym; void bpf_kfunc_call_test_offset(struct prog_test_ref_kfunc *p); struct prog_test_member *bpf_kfunc_call_memb_acquire(void); -- 2.30.2