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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id t22sm4401685pfg.63.2021.10.26.15.27.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Oct 2021 15:27:50 -0700 (PDT) From: Joe Burton To: Andrii Nakryiko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, trivial@kernel.org, Joe Burton Subject: [PATCH] libbpf: Deprecate bpf_objects_list Date: Tue, 26 Oct 2021 22:27:46 +0000 Message-Id: <20211026222746.403866-1-jevburton.kernel@gmail.com> X-Mailer: git-send-email 2.33.0.1079.g6e70778dc9-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Joe Burton Add a flag to `enum libbpf_strict_mode' to disable the global `bpf_objects_list', preventing race conditions when concurrent threads call bpf_object__open() or bpf_object__close(). bpf_object__next() will return NULL if this option is set. Callers may achieve the same workflow by tracking bpf_objects in application code. [0] Closes: https://github.com/libbpf/libbpf/issues/293 Signed-off-by: Joe Burton --- tools/lib/bpf/libbpf.c | 8 +++++++- tools/lib/bpf/libbpf.h | 3 ++- tools/lib/bpf/libbpf_legacy.h | 6 ++++++ 3 files changed, 15 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 2fbed2d4a645..59d39ce9f375 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1148,6 +1148,7 @@ static struct bpf_object *bpf_object__new(const char *path, size_t obj_buf_sz, const char *obj_name) { + bool strict = (libbpf_mode & LIBBPF_STRICT_NO_OBJECT_LIST); struct bpf_object *obj; char *end; @@ -1188,7 +1189,8 @@ static struct bpf_object *bpf_object__new(const char *path, obj->loaded = false; INIT_LIST_HEAD(&obj->list); - list_add(&obj->list, &bpf_objects_list); + if (!strict) + list_add(&obj->list, &bpf_objects_list); return obj; } @@ -7935,6 +7937,10 @@ struct bpf_object * bpf_object__next(struct bpf_object *prev) { struct bpf_object *next; + bool strict = (libbpf_mode & LIBBPF_STRICT_NO_OBJECT_LIST); + + if (strict) + return NULL; if (!prev) next = list_first_entry(&bpf_objects_list, diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index e1900819bfab..defabdbe7760 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -168,7 +168,8 @@ LIBBPF_API struct bpf_program * bpf_object__find_program_by_name(const struct bpf_object *obj, const char *name); -LIBBPF_API struct bpf_object *bpf_object__next(struct bpf_object *prev); +LIBBPF_API LIBBPF_DEPRECATED_SINCE(0, 7, "track bpf_objects in application code instead") +struct bpf_object *bpf_object__next(struct bpf_object *prev); #define bpf_object__for_each_safe(pos, tmp) \ for ((pos) = bpf_object__next(NULL), \ (tmp) = bpf_object__next(pos); \ diff --git a/tools/lib/bpf/libbpf_legacy.h b/tools/lib/bpf/libbpf_legacy.h index 29ccafab11a8..5ba5c9beccfa 100644 --- a/tools/lib/bpf/libbpf_legacy.h +++ b/tools/lib/bpf/libbpf_legacy.h @@ -57,6 +57,12 @@ enum libbpf_strict_mode { * function name instead of section name. */ LIBBPF_STRICT_SEC_NAME = 0x04, + /* + * Disable the global 'bpf_objects_list'. Maintaining this list adds + * a race condition to bpf_object__open() and bpf_object__close(). + * Clients can maintain it on their own if it is valuable for them. + */ + LIBBPF_STRICT_NO_OBJECT_LIST = 0x08, __LIBBPF_STRICT_LAST, }; -- 2.33.0.1079.g6e70778dc9-goog