Re: [PATCH v1] perf env: Avoid recursively taking env->bpf_progs.lock

From: Ian Rogers
Date: Wed Jan 03 2024 - 11:24:52 EST

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In reply to: Arnaldo Carvalho de Melo: "Re: [PATCH v1] perf env: Avoid recursively taking env->bpf_progs.lock"
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On Wed, Jan 3, 2024 at 8:09 AM Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
>
> Em Wed, Dec 06, 2023 at 05:46:55PM -0800, Ian Rogers escreveu:
> > 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@xxxxxxxxxx>
> > ---
> > Previously this patch was part of a larger set:
> > https://lore.kernel.org/lkml/20231127220902.1315692-51-irogers@xxxxxxxxxx/
> > ---
> > 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);
> > +}
>
> Minor nit/modification:
>
> diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
> index cfdacbf294566c33..a459374d0a1a1dc8 100644
> --- a/tools/perf/util/env.c
> +++ b/tools/perf/util/env.c
> @@ -22,7 +22,8 @@ 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);
>
> Just to reduce patch size a bit, just like happened with
> perf_env__insert_btf() further down, where its body was changed to call
> the __ variant but the non __ function got just the body modified.
>
> - Arnaldo

Sorry for that and thanks for the fix.

Ian

> > +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
> >
>
> --
>
> - Arnaldo

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