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Message-ID: <aKMuENl9omxi6OwJ@krava>
Date: Mon, 18 Aug 2025 15:43:44 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: mhiramat@...nel.org, rostedt@...dmis.org,
mathieu.desnoyers@...icios.com, hca@...ux.ibm.com,
revest@...omium.org, linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v5 1/4] fprobe: use rhltable for fprobe_ip_table
On Sun, Aug 17, 2025 at 10:46:02AM +0800, Menglong Dong wrote:
SNIP
> +/* Node insertion and deletion requires the fprobe_mutex */
> +static int insert_fprobe_node(struct fprobe_hlist_node *node)
> +{
> lockdep_assert_held(&fprobe_mutex);
>
> - next = find_first_fprobe_node(ip);
> - if (next) {
> - hlist_add_before_rcu(&node->hlist, &next->hlist);
> - return;
> - }
> - head = &fprobe_ip_table[hash_ptr((void *)ip, FPROBE_IP_HASH_BITS)];
> - hlist_add_head_rcu(&node->hlist, head);
> + return rhltable_insert(&fprobe_ip_table, &node->hlist, fprobe_rht_params);
> }
>
> /* Return true if there are synonims */
> @@ -92,9 +92,11 @@ static bool delete_fprobe_node(struct fprobe_hlist_node *node)
> /* Avoid double deleting */
> if (READ_ONCE(node->fp) != NULL) {
> WRITE_ONCE(node->fp, NULL);
> - hlist_del_rcu(&node->hlist);
> + rhltable_remove(&fprobe_ip_table, &node->hlist,
> + fprobe_rht_params);
> }
> - return !!find_first_fprobe_node(node->addr);
> + return !!rhltable_lookup(&fprobe_ip_table, &node->addr,
> + fprobe_rht_params);
I think rhltable_lookup needs rcu lock
> }
>
> /* Check existence of the fprobe */
> @@ -249,9 +251,10 @@ static inline int __fprobe_kprobe_handler(unsigned long ip, unsigned long parent
> static int fprobe_entry(struct ftrace_graph_ent *trace, struct fgraph_ops *gops,
> struct ftrace_regs *fregs)
> {
> - struct fprobe_hlist_node *node, *first;
> unsigned long *fgraph_data = NULL;
> unsigned long func = trace->func;
> + struct fprobe_hlist_node *node;
> + struct rhlist_head *head, *pos;
> unsigned long ret_ip;
> int reserved_words;
> struct fprobe *fp;
> @@ -260,14 +263,11 @@ static int fprobe_entry(struct ftrace_graph_ent *trace, struct fgraph_ops *gops,
> if (WARN_ON_ONCE(!fregs))
> return 0;
>
> - first = node = find_first_fprobe_node(func);
> - if (unlikely(!first))
> - return 0;
> -
> + head = rhltable_lookup(&fprobe_ip_table, &func, fprobe_rht_params);
ditto
jirka
> reserved_words = 0;
> - hlist_for_each_entry_from_rcu(node, hlist) {
> + rhl_for_each_entry_rcu(node, pos, head, hlist) {
> if (node->addr != func)
> - break;
> + continue;
> fp = READ_ONCE(node->fp);
> if (!fp || !fp->exit_handler)
> continue;
> @@ -278,13 +278,12 @@ static int fprobe_entry(struct ftrace_graph_ent *trace, struct fgraph_ops *gops,
> reserved_words +=
> FPROBE_HEADER_SIZE_IN_LONG + SIZE_IN_LONG(fp->entry_data_size);
> }
> - node = first;
> if (reserved_words) {
> fgraph_data = fgraph_reserve_data(gops->idx, reserved_words * sizeof(long));
> if (unlikely(!fgraph_data)) {
> - hlist_for_each_entry_from_rcu(node, hlist) {
> + rhl_for_each_entry_rcu(node, pos, head, hlist) {
> if (node->addr != func)
> - break;
> + continue;
> fp = READ_ONCE(node->fp);
> if (fp && !fprobe_disabled(fp))
> fp->nmissed++;
> @@ -299,12 +298,12 @@ static int fprobe_entry(struct ftrace_graph_ent *trace, struct fgraph_ops *gops,
> */
> ret_ip = ftrace_regs_get_return_address(fregs);
> used = 0;
> - hlist_for_each_entry_from_rcu(node, hlist) {
> + rhl_for_each_entry_rcu(node, pos, head, hlist) {
> int data_size;
> void *data;
>
> if (node->addr != func)
> - break;
> + continue;
> fp = READ_ONCE(node->fp);
> if (!fp || fprobe_disabled(fp))
> continue;
> @@ -448,25 +447,21 @@ static int fprobe_addr_list_add(struct fprobe_addr_list *alist, unsigned long ad
> return 0;
> }
>
> -static void fprobe_remove_node_in_module(struct module *mod, struct hlist_head *head,
> - struct fprobe_addr_list *alist)
> +static void fprobe_remove_node_in_module(struct module *mod, struct fprobe_hlist_node *node,
> + struct fprobe_addr_list *alist)
> {
> - struct fprobe_hlist_node *node;
> int ret = 0;
>
> - hlist_for_each_entry_rcu(node, head, hlist,
> - lockdep_is_held(&fprobe_mutex)) {
> - if (!within_module(node->addr, mod))
> - continue;
> - if (delete_fprobe_node(node))
> - continue;
> - /*
> - * If failed to update alist, just continue to update hlist.
> - * Therefore, at list user handler will not hit anymore.
> - */
> - if (!ret)
> - ret = fprobe_addr_list_add(alist, node->addr);
> - }
> + if (!within_module(node->addr, mod))
> + return;
> + if (delete_fprobe_node(node))
> + return;
> + /*
> + * If failed to update alist, just continue to update hlist.
> + * Therefore, at list user handler will not hit anymore.
> + */
> + if (!ret)
> + ret = fprobe_addr_list_add(alist, node->addr);
> }
>
> /* Handle module unloading to manage fprobe_ip_table. */
> @@ -474,8 +469,9 @@ static int fprobe_module_callback(struct notifier_block *nb,
> unsigned long val, void *data)
> {
> struct fprobe_addr_list alist = {.size = FPROBE_IPS_BATCH_INIT};
> + struct fprobe_hlist_node *node;
> + struct rhashtable_iter iter;
> struct module *mod = data;
> - int i;
>
> if (val != MODULE_STATE_GOING)
> return NOTIFY_DONE;
> @@ -486,8 +482,16 @@ static int fprobe_module_callback(struct notifier_block *nb,
> return NOTIFY_DONE;
>
> mutex_lock(&fprobe_mutex);
> - for (i = 0; i < FPROBE_IP_TABLE_SIZE; i++)
> - fprobe_remove_node_in_module(mod, &fprobe_ip_table[i], &alist);
> + rhltable_walk_enter(&fprobe_ip_table, &iter);
> + do {
> + rhashtable_walk_start(&iter);
> +
> + while ((node = rhashtable_walk_next(&iter)) && !IS_ERR(node))
> + fprobe_remove_node_in_module(mod, node, &alist);
> +
> + rhashtable_walk_stop(&iter);
> + } while (node == ERR_PTR(-EAGAIN));
> + rhashtable_walk_exit(&iter);
>
> if (alist.index < alist.size && alist.index > 0)
> ftrace_set_filter_ips(&fprobe_graph_ops.ops,
> @@ -727,8 +731,16 @@ int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num)
> ret = fprobe_graph_add_ips(addrs, num);
> if (!ret) {
> add_fprobe_hash(fp);
> - for (i = 0; i < hlist_array->size; i++)
> - insert_fprobe_node(&hlist_array->array[i]);
> + for (i = 0; i < hlist_array->size; i++) {
> + ret = insert_fprobe_node(&hlist_array->array[i]);
> + if (ret)
> + break;
> + }
> + /* fallback on insert error */
> + if (ret) {
> + for (i--; i >= 0; i--)
> + delete_fprobe_node(&hlist_array->array[i]);
> + }
> }
> mutex_unlock(&fprobe_mutex);
>
> @@ -824,3 +836,10 @@ int unregister_fprobe(struct fprobe *fp)
> return ret;
> }
> EXPORT_SYMBOL_GPL(unregister_fprobe);
> +
> +static int __init fprobe_initcall(void)
> +{
> + rhltable_init(&fprobe_ip_table, &fprobe_rht_params);
> + return 0;
> +}
> +late_initcall(fprobe_initcall);
> --
> 2.50.1
>
>
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