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References: <20231207014655.1252484-1-irogers@google.com>
In-Reply-To: <20231207014655.1252484-1-irogers@google.com>
From: Ian Rogers <irogers@google.com>
Date: Tue, 2 Jan 2024 19:00:53 -0800
Message-ID: <CAP-5=fWdAouBb7us44HOdd+ZfBj5fLFTuLCokbG8w3jVuQgTxw@mail.gmail.com>
Subject: Re: [PATCH v1] perf env: Avoid recursively taking env->bpf_progs.lock
To: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, 
	Arnaldo Carvalho de Melo <acme@kernel.org>, Mark Rutland <mark.rutland@arm.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>, 
	Namhyung Kim <namhyung@kernel.org>, Ian Rogers <irogers@google.com>, 
	Adrian Hunter <adrian.hunter@intel.com>, Song Liu <song@kernel.org>, 
	Ming Wang <wangming01@loongson.cn>, Ravi Bangoria <ravi.bangoria@amd.com>, 
	Huacai Chen <chenhuacai@kernel.org>, Kan Liang <kan.liang@linux.intel.com>, 
	K Prateek Nayak <kprateek.nayak@amd.com>, linux-perf-users@vger.kernel.org, 
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org
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On Wed, Dec 6, 2023 at 5:46=E2=80=AFPM Ian Rogers <irogers@google.com> wrot=
e:
>
> 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@google.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, s=
truct 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 =3D (__u32 *)(uintptr_t)(info->jited_func_lens);
>         __u64 *prog_addrs =3D (__u64 *)(uintptr_t)(info->jited_ksyms);
> @@ -563,7 +563,7 @@ void bpf_event__print_bpf_prog_info(struct bpf_prog_i=
nfo *info,
>         if (info->btf_id) {
>                 struct btf_node *node;
>
> -               node =3D perf_env__find_btf(env, info->btf_id);
> +               node =3D __perf_env__find_btf(env, info->btf_id);
>                 if (node)
>                         btf =3D 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 *even=
t,
>                          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_u=
nused,
>                                        union perf_event *event __maybe_un=
used,
> @@ -50,9 +50,9 @@ static inline int evlist__add_bpf_sb_event(struct evlis=
t *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_unus=
ed)
>  {
>
>  }
> 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_pro=
g_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_p=
rog_info_node *info_node)
>  {
>         __u32 prog_id =3D info_node->info_linear->info.id;
>         struct bpf_prog_info_node *node;
>         struct rb_node *parent =3D NULL;
>         struct rb_node **p;
>
> -       down_write(&env->bpf_progs.lock);
>         p =3D &env->bpf_progs.infos.rb_node;
>
>         while (*p !=3D NULL) {
> @@ -42,15 +47,13 @@ void perf_env__insert_bpf_prog_info(struct perf_env *=
env,
>                         p =3D &(*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_in=
fo(struct perf_env *env,
>  }
>
>  bool perf_env__insert_btf(struct perf_env *env, struct btf_node *btf_nod=
e)
> +{
> +       bool ret;
> +
> +       down_write(&env->bpf_progs.lock);
> +       ret =3D __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_n=
ode)
>  {
>         struct rb_node *parent =3D NULL;
>         __u32 btf_id =3D btf_node->id;
>         struct btf_node *node;
>         struct rb_node **p;
> -       bool ret =3D true;
>
> -       down_write(&env->bpf_progs.lock);
>         p =3D &env->bpf_progs.btfs.rb_node;
>
>         while (*p !=3D NULL) {
> @@ -98,25 +109,31 @@ bool perf_env__insert_btf(struct perf_env *env, stru=
ct btf_node *btf_node)
>                         p =3D &(*p)->rb_right;
>                 } else {
>                         pr_debug("duplicated btf %u\n", btf_id);
> -                       ret =3D 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 =3D __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 =3D NULL;
>         struct rb_node *n;
>
> -       down_read(&env->bpf_progs.lock);
>         n =3D 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 =3D n->rb_right;
>                 else
> -                       goto out;
> +                       return node;
>         }
> -       node =3D 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_nod=
e);
>  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_nod=
e);
> +bool __perf_env__insert_btf(struct perf_env *env, struct btf_node *btf_n=
ode);
>  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 =3D rb_entry(next, struct bpf_prog_info_node, rb_nod=
e);
>                 next =3D 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 =3D 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 =3D NULL;
>         }
>
> --
> 2.43.0.rc2.451.g8631bc7472-goog
>