diff options
| author | JP Kobryn <inwardvessel@gmail.com> | 2023-03-24 18:08:45 -0700 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2023-03-27 11:33:43 -0700 |
| commit | f1cb927cdb6280e0ce283174cc1bf395dffc43d4 (patch) | |
| tree | d9797bbb0073a28680c76bf7fe862a4272d5a285 | |
| parent | 5f5a7d8d8bd461f515543040ad7d107cc405d30c (diff) | |
| download | bpf-f1cb927cdb6280e0ce283174cc1bf395dffc43d4.tar.gz | |
libbpf: Ensure print callback usage is thread-safe
This patch prevents races on the print function pointer, allowing the
libbpf_set_print() function to become thread-safe.
Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230325010845.46000-1-inwardvessel@gmail.com
| -rw-r--r-- | tools/lib/bpf/libbpf.c | 9 | ||||
| -rw-r--r-- | tools/lib/bpf/libbpf.h | 2 |
2 files changed, 8 insertions, 3 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index f6a071db5c6e59..15737d7b5a2889 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -216,9 +216,10 @@ static libbpf_print_fn_t __libbpf_pr = __base_pr; libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn) { - libbpf_print_fn_t old_print_fn = __libbpf_pr; + libbpf_print_fn_t old_print_fn; + + old_print_fn = __atomic_exchange_n(&__libbpf_pr, fn, __ATOMIC_RELAXED); - __libbpf_pr = fn; return old_print_fn; } @@ -227,8 +228,10 @@ void libbpf_print(enum libbpf_print_level level, const char *format, ...) { va_list args; int old_errno; + libbpf_print_fn_t print_fn; - if (!__libbpf_pr) + print_fn = __atomic_load_n(&__libbpf_pr, __ATOMIC_RELAXED); + if (!print_fn) return; old_errno = errno; diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 1615e55e2e7907..0b7362397ea34a 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -101,6 +101,8 @@ typedef int (*libbpf_print_fn_t)(enum libbpf_print_level level, * be used for libbpf warnings and informational messages. * @param fn The log print function. If NULL, libbpf won't print anything. * @return Pointer to old print function. + * + * This function is thread-safe. */ LIBBPF_API libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn); |