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// SPDX-License-Identifier: GPL-2.0
/* Exercise re-entry into call_srcu() from BPF; see progs/rcu_reentry.c. */
#define _GNU_SOURCE
#include <sched.h>
#include <test_progs.h>
#include "task_local_storage_helpers.h"
#include "trace_helpers.h"
#include "rcu_reentry.skel.h"
/* Tiny RCU has no rcu_segcblist_enqueue() to attach to. */
static bool have_attach_target(void)
{
unsigned long long addr;
return kallsyms_find("rcu_segcblist_enqueue", &addr) == 0;
}
/* Tiny SRCU stubs out srcu_expedite_current(); Tree SRCU exports it. */
static bool have_tree_srcu(void)
{
unsigned long long addr;
return kallsyms_find("srcu_expedite_current", &addr) == 0;
}
void test_rcu_reentry(void)
{
struct rcu_reentry *skel;
int err, pidfd = -1, map_fd;
cpu_set_t set, old_set;
bool affinity_saved;
__u64 val = 1;
int cpu;
if (!have_attach_target()) {
test__skip();
return;
}
skel = rcu_reentry__open_and_load();
if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
return;
err = rcu_reentry__attach(skel);
if (!ASSERT_OK(err, "skel_attach"))
goto out;
/* Keep the re-entry on a single CPU; a cpuset may exclude CPU 0. */
affinity_saved = !sched_getaffinity(0, sizeof(old_set), &old_set);
cpu = sched_getcpu();
if (!ASSERT_GE(cpu, 0, "getcpu"))
goto out;
CPU_ZERO(&set);
CPU_SET(cpu, &set);
if (!ASSERT_OK(sched_setaffinity(0, sizeof(set), &set), "setaffinity"))
goto out;
pidfd = sys_pidfd_open(getpid(), 0);
if (!ASSERT_GE(pidfd, 0, "pidfd_open"))
goto restore;
map_fd = bpf_map__fd(skel->maps.task_stg);
err = bpf_map_update_elem(map_fd, &pidfd, &val, BPF_NOEXIST);
if (!ASSERT_OK(err, "boot_create"))
goto restore;
/* Arm the handler for this thread, then trigger call_rcu_tasks_trace(). */
skel->bss->target_pid = syscall(__NR_gettid);
err = bpf_map_delete_elem(map_fd, &pidfd);
if (!ASSERT_OK(err, "boot_delete"))
goto restore;
/*
* Only Tree SRCU reaches rcu_segcblist_enqueue() from call_srcu(); a
* UP+PREEMPT kernel pairs Tree RCU with Tiny SRCU, so the attach
* succeeds but nothing fires. On Tree SRCU it must fire.
*/
if (!skel->bss->hits) {
if (have_tree_srcu())
ASSERT_GT(skel->bss->hits, 0, "prog_fired");
else
test__skip();
goto restore;
}
ASSERT_EQ(skel->bss->get_errs, 0, "nested_storage_get");
ASSERT_EQ(skel->bss->del_errs, 0, "nested_storage_delete");
restore:
if (affinity_saved)
sched_setaffinity(0, sizeof(old_set), &old_set);
out:
if (pidfd >= 0)
close(pidfd);
rcu_reentry__destroy(skel);
}
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