[PATCH v5 50/50] perf env: Avoid recursively taking env->bpf_progs.lock

From: Ian Rogers
Date: Mon Nov 27 2023 - 17:16:27 EST

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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>
---
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 b564d6fd078a..827695cd0408 100644
--- a/tools/perf/util/bpf-event.c
+++ b/tools/perf/util/bpf-event.c
@@ -546,9 +546,9 @@ 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);
@@ -564,7 +564,7 @@ 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 cbc18b22ace5..cb39886b2e81 100644
--- a/tools/perf/util/env.c
+++ b/tools/perf/util/env.c
@@ -20,15 +20,20 @@ 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) {
@@ -40,15 +45,13 @@ 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,
@@ -77,14 +80,22 @@ 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) {
@@ -96,25 +107,31 @@ 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) {
@@ -124,13 +141,9 @@ 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 94596ff124d5..63a4486187b0 100644
--- a/tools/perf/util/env.h
+++ b/tools/perf/util/env.h
@@ -169,12 +169,16 @@ 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 da4ddc4bdc84..4fcfd1ace6af 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1848,8 +1848,8 @@ 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);
@@ -3187,7 +3187,7 @@ 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);
@@ -3234,7 +3234,7 @@ 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.rc1.413.gea7ed67945-goog

Next message: Ian Rogers: "[PATCH v5 49/50] perf dso: Use container_of to avoid a pointer in dso_data"
Previous message: Ian Rogers: "[PATCH v5 46/50] perf dsos: Switch hand code to bsearch"
In reply to: Ian Rogers: "[PATCH v5 46/50] perf dsos: Switch hand code to bsearch"
Next in thread: Ian Rogers: "[PATCH v5 49/50] perf dso: Use container_of to avoid a pointer in dso_data"
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