linux/tools/perf/util/bpf_lock_contention.c

// SPDX-License-Identifier: GPL-2.0
#include "util/debug.h"
#include "util/machine.h"
#include "util/map.h"
#include "util/symbol.h"
#include "util/lock-contention.h"
#include <linux/zalloc.h>
#include <bpf/bpf.h>

#include "bpf_skel/lock_contention.skel.h"

static struct lock_contention_bpf *skel;

/* should be same as bpf_skel/lock_contention.bpf.c */
struct lock_contention_key {
	u32 stack_id;
};

struct lock_contention_data {
	u64 total_time;
	u64 min_time;
	u64 max_time;
	u32 count;
	u32 flags;
};

int lock_contention_prepare(void)
{
	skel = lock_contention_bpf__open();
	if (!skel) {
		pr_err("Failed to open lock-contention BPF skeleton\n");
		return -1;
	}

	if (lock_contention_bpf__load(skel) < 0) {
		pr_err("Failed to load lock-contention BPF skeleton\n");
		return -1;
	}

	lock_contention_bpf__attach(skel);
	return 0;
}

int lock_contention_start(void)
{
	skel->bss->enabled = 1;
	return 0;
}

int lock_contention_stop(void)
{
	skel->bss->enabled = 0;
	return 0;
}

int lock_contention_read(struct machine *machine, struct hlist_head *head)
{
	int fd, stack;
	u32 prev_key, key;
	struct lock_contention_data data;
	struct lock_stat *st;
	u64 stack_trace[CONTENTION_STACK_DEPTH];

	fd = bpf_map__fd(skel->maps.lock_stat);
	stack = bpf_map__fd(skel->maps.stacks);

	prev_key = 0;
	while (!bpf_map_get_next_key(fd, &prev_key, &key)) {
		struct map *kmap;
		struct symbol *sym;
		int idx;

		bpf_map_lookup_elem(fd, &key, &data);
		st = zalloc(sizeof(*st));
		if (st == NULL)
			return -1;

		st->nr_contended = data.count;
		st->wait_time_total = data.total_time;
		st->wait_time_max = data.max_time;
		st->wait_time_min = data.min_time;

		if (data.count)
			st->avg_wait_time = data.total_time / data.count;

		st->flags = data.flags;

		bpf_map_lookup_elem(stack, &key, stack_trace);

		/* skip BPF + lock internal functions */
		idx = CONTENTION_STACK_SKIP;
		while (is_lock_function(machine, stack_trace[idx]) &&
		       idx < CONTENTION_STACK_DEPTH - 1)
			idx++;

		st->addr = stack_trace[idx];
		sym = machine__find_kernel_symbol(machine, st->addr, &kmap);

		if (sym) {
			unsigned long offset;
			int ret = 0;

			offset = kmap->map_ip(kmap, st->addr) - sym->start;

			if (offset)
				ret = asprintf(&st->name, "%s+%#lx", sym->name, offset);
			else
				st->name = strdup(sym->name);

			if (ret < 0 || st->name == NULL)
				return -1;
		} else if (asprintf(&st->name, "%#lx", (unsigned long)st->addr) < 0) {
			free(st);
			return -1;
		}

		hlist_add_head(&st->hash_entry, head);
		prev_key = key;
	}

	return 0;
}

int lock_contention_finish(void)
{
	if (skel) {
		skel->bss->enabled = 0;
		lock_contention_bpf__destroy(skel);
	}

	return 0;
}