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Message-ID: <CAP-5=fWdAouBb7us44HOdd+ZfBj5fLFTuLCokbG8w3jVuQgTxw@mail.gmail.com>
Date: Tue, 2 Jan 2024 19:00:53 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>, Song Liu <song@...nel.org>,
Ming Wang <wangming01@...ngson.cn>, Ravi Bangoria <ravi.bangoria@....com>,
Huacai Chen <chenhuacai@...nel.org>, Kan Liang <kan.liang@...ux.intel.com>,
K Prateek Nayak <kprateek.nayak@....com>, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v1] perf env: Avoid recursively taking env->bpf_progs.lock
On Wed, Dec 6, 2023 at 5:46 PM Ian Rogers <irogers@...gle.com> wrote:
>
> Add variants of perf_env__insert_bpf_prog_info, perf_env__insert_btf
> and perf_env__find_btf prefixed with __ to indicate the
> env->bpf_progs.lock is assumed held. Call these variants when the lock
> is held to avoid recursively taking it and potentially having a thread
> deadlock with itself.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
Ping.
Thanks,
Ian
> ---
> Previously this patch was part of a larger set:
> https://lore.kernel.org/lkml/20231127220902.1315692-51-irogers@google.com/
> ---
> tools/perf/util/bpf-event.c | 8 +++---
> tools/perf/util/bpf-event.h | 12 ++++-----
> tools/perf/util/env.c | 53 +++++++++++++++++++++++--------------
> tools/perf/util/env.h | 4 +++
> tools/perf/util/header.c | 8 +++---
> 5 files changed, 51 insertions(+), 34 deletions(-)
>
> diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
> index 830711cae30d..3573e0b7ef3e 100644
> --- a/tools/perf/util/bpf-event.c
> +++ b/tools/perf/util/bpf-event.c
> @@ -545,9 +545,9 @@ int evlist__add_bpf_sb_event(struct evlist *evlist, struct perf_env *env)
> return evlist__add_sb_event(evlist, &attr, bpf_event__sb_cb, env);
> }
>
> -void bpf_event__print_bpf_prog_info(struct bpf_prog_info *info,
> - struct perf_env *env,
> - FILE *fp)
> +void __bpf_event__print_bpf_prog_info(struct bpf_prog_info *info,
> + struct perf_env *env,
> + FILE *fp)
> {
> __u32 *prog_lens = (__u32 *)(uintptr_t)(info->jited_func_lens);
> __u64 *prog_addrs = (__u64 *)(uintptr_t)(info->jited_ksyms);
> @@ -563,7 +563,7 @@ void bpf_event__print_bpf_prog_info(struct bpf_prog_info *info,
> if (info->btf_id) {
> struct btf_node *node;
>
> - node = perf_env__find_btf(env, info->btf_id);
> + node = __perf_env__find_btf(env, info->btf_id);
> if (node)
> btf = btf__new((__u8 *)(node->data),
> node->data_size);
> diff --git a/tools/perf/util/bpf-event.h b/tools/perf/util/bpf-event.h
> index 1bcbd4fb6c66..e2f0420905f5 100644
> --- a/tools/perf/util/bpf-event.h
> +++ b/tools/perf/util/bpf-event.h
> @@ -33,9 +33,9 @@ struct btf_node {
> int machine__process_bpf(struct machine *machine, union perf_event *event,
> struct perf_sample *sample);
> int evlist__add_bpf_sb_event(struct evlist *evlist, struct perf_env *env);
> -void bpf_event__print_bpf_prog_info(struct bpf_prog_info *info,
> - struct perf_env *env,
> - FILE *fp);
> +void __bpf_event__print_bpf_prog_info(struct bpf_prog_info *info,
> + struct perf_env *env,
> + FILE *fp);
> #else
> static inline int machine__process_bpf(struct machine *machine __maybe_unused,
> union perf_event *event __maybe_unused,
> @@ -50,9 +50,9 @@ static inline int evlist__add_bpf_sb_event(struct evlist *evlist __maybe_unused,
> return 0;
> }
>
> -static inline void bpf_event__print_bpf_prog_info(struct bpf_prog_info *info __maybe_unused,
> - struct perf_env *env __maybe_unused,
> - FILE *fp __maybe_unused)
> +static inline void __bpf_event__print_bpf_prog_info(struct bpf_prog_info *info __maybe_unused,
> + struct perf_env *env __maybe_unused,
> + FILE *fp __maybe_unused)
> {
>
> }
> diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
> index c68b7a004f29..cfdacbf29456 100644
> --- a/tools/perf/util/env.c
> +++ b/tools/perf/util/env.c
> @@ -22,15 +22,20 @@ struct perf_env perf_env;
> #include "bpf-utils.h"
> #include <bpf/libbpf.h>
>
> -void perf_env__insert_bpf_prog_info(struct perf_env *env,
> - struct bpf_prog_info_node *info_node)
> +void perf_env__insert_bpf_prog_info(struct perf_env *env, struct bpf_prog_info_node *info_node)
> +{
> + down_write(&env->bpf_progs.lock);
> + __perf_env__insert_bpf_prog_info(env, info_node);
> + up_write(&env->bpf_progs.lock);
> +}
> +
> +void __perf_env__insert_bpf_prog_info(struct perf_env *env, struct bpf_prog_info_node *info_node)
> {
> __u32 prog_id = info_node->info_linear->info.id;
> struct bpf_prog_info_node *node;
> struct rb_node *parent = NULL;
> struct rb_node **p;
>
> - down_write(&env->bpf_progs.lock);
> p = &env->bpf_progs.infos.rb_node;
>
> while (*p != NULL) {
> @@ -42,15 +47,13 @@ void perf_env__insert_bpf_prog_info(struct perf_env *env,
> p = &(*p)->rb_right;
> } else {
> pr_debug("duplicated bpf prog info %u\n", prog_id);
> - goto out;
> + return;
> }
> }
>
> rb_link_node(&info_node->rb_node, parent, p);
> rb_insert_color(&info_node->rb_node, &env->bpf_progs.infos);
> env->bpf_progs.infos_cnt++;
> -out:
> - up_write(&env->bpf_progs.lock);
> }
>
> struct bpf_prog_info_node *perf_env__find_bpf_prog_info(struct perf_env *env,
> @@ -79,14 +82,22 @@ struct bpf_prog_info_node *perf_env__find_bpf_prog_info(struct perf_env *env,
> }
>
> bool perf_env__insert_btf(struct perf_env *env, struct btf_node *btf_node)
> +{
> + bool ret;
> +
> + down_write(&env->bpf_progs.lock);
> + ret = __perf_env__insert_btf(env, btf_node);
> + up_write(&env->bpf_progs.lock);
> + return ret;
> +}
> +
> +bool __perf_env__insert_btf(struct perf_env *env, struct btf_node *btf_node)
> {
> struct rb_node *parent = NULL;
> __u32 btf_id = btf_node->id;
> struct btf_node *node;
> struct rb_node **p;
> - bool ret = true;
>
> - down_write(&env->bpf_progs.lock);
> p = &env->bpf_progs.btfs.rb_node;
>
> while (*p != NULL) {
> @@ -98,25 +109,31 @@ bool perf_env__insert_btf(struct perf_env *env, struct btf_node *btf_node)
> p = &(*p)->rb_right;
> } else {
> pr_debug("duplicated btf %u\n", btf_id);
> - ret = false;
> - goto out;
> + return false;
> }
> }
>
> rb_link_node(&btf_node->rb_node, parent, p);
> rb_insert_color(&btf_node->rb_node, &env->bpf_progs.btfs);
> env->bpf_progs.btfs_cnt++;
> -out:
> - up_write(&env->bpf_progs.lock);
> - return ret;
> + return true;
> }
>
> struct btf_node *perf_env__find_btf(struct perf_env *env, __u32 btf_id)
> +{
> + struct btf_node *res;
> +
> + down_read(&env->bpf_progs.lock);
> + res = __perf_env__find_btf(env, btf_id);
> + up_read(&env->bpf_progs.lock);
> + return res;
> +}
> +
> +struct btf_node *__perf_env__find_btf(struct perf_env *env, __u32 btf_id)
> {
> struct btf_node *node = NULL;
> struct rb_node *n;
>
> - down_read(&env->bpf_progs.lock);
> n = env->bpf_progs.btfs.rb_node;
>
> while (n) {
> @@ -126,13 +143,9 @@ struct btf_node *perf_env__find_btf(struct perf_env *env, __u32 btf_id)
> else if (btf_id > node->id)
> n = n->rb_right;
> else
> - goto out;
> + return node;
> }
> - node = NULL;
> -
> -out:
> - up_read(&env->bpf_progs.lock);
> - return node;
> + return NULL;
> }
>
> /* purge data in bpf_progs.infos tree */
> diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
> index bf7e3c4c211f..7c527e65c186 100644
> --- a/tools/perf/util/env.h
> +++ b/tools/perf/util/env.h
> @@ -175,12 +175,16 @@ const char *perf_env__raw_arch(struct perf_env *env);
> int perf_env__nr_cpus_avail(struct perf_env *env);
>
> void perf_env__init(struct perf_env *env);
> +void __perf_env__insert_bpf_prog_info(struct perf_env *env,
> + struct bpf_prog_info_node *info_node);
> void perf_env__insert_bpf_prog_info(struct perf_env *env,
> struct bpf_prog_info_node *info_node);
> struct bpf_prog_info_node *perf_env__find_bpf_prog_info(struct perf_env *env,
> __u32 prog_id);
> bool perf_env__insert_btf(struct perf_env *env, struct btf_node *btf_node);
> +bool __perf_env__insert_btf(struct perf_env *env, struct btf_node *btf_node);
> struct btf_node *perf_env__find_btf(struct perf_env *env, __u32 btf_id);
> +struct btf_node *__perf_env__find_btf(struct perf_env *env, __u32 btf_id);
>
> int perf_env__numa_node(struct perf_env *env, struct perf_cpu cpu);
> char *perf_env__find_pmu_cap(struct perf_env *env, const char *pmu_name,
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 08cc2febabde..02bf9d8b5f74 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1849,8 +1849,8 @@ static void print_bpf_prog_info(struct feat_fd *ff, FILE *fp)
> node = rb_entry(next, struct bpf_prog_info_node, rb_node);
> next = rb_next(&node->rb_node);
>
> - bpf_event__print_bpf_prog_info(&node->info_linear->info,
> - env, fp);
> + __bpf_event__print_bpf_prog_info(&node->info_linear->info,
> + env, fp);
> }
>
> up_read(&env->bpf_progs.lock);
> @@ -3188,7 +3188,7 @@ static int process_bpf_prog_info(struct feat_fd *ff, void *data __maybe_unused)
> /* after reading from file, translate offset to address */
> bpil_offs_to_addr(info_linear);
> info_node->info_linear = info_linear;
> - perf_env__insert_bpf_prog_info(env, info_node);
> + __perf_env__insert_bpf_prog_info(env, info_node);
> }
>
> up_write(&env->bpf_progs.lock);
> @@ -3235,7 +3235,7 @@ static int process_bpf_btf(struct feat_fd *ff, void *data __maybe_unused)
> if (__do_read(ff, node->data, data_size))
> goto out;
>
> - perf_env__insert_btf(env, node);
> + __perf_env__insert_btf(env, node);
> node = NULL;
> }
>
> --
> 2.43.0.rc2.451.g8631bc7472-goog
>
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