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authorJP Kobryn <inwardvessel@gmail.com>2023-03-24 18:08:45 -0700
committerAndrii Nakryiko <andrii@kernel.org>2023-03-27 11:33:43 -0700
commitf1cb927cdb6280e0ce283174cc1bf395dffc43d4 (patch)
treed9797bbb0073a28680c76bf7fe862a4272d5a285 /tools/lib
parent5f5a7d8d8bd461f515543040ad7d107cc405d30c (diff)
downloadlinux-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
Diffstat (limited to 'tools/lib')
-rw-r--r--tools/lib/bpf/libbpf.c9
-rw-r--r--tools/lib/bpf/libbpf.h2
2 files changed, 8 insertions, 3 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index f6a071db5c6e..15737d7b5a28 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 1615e55e2e79..0b7362397ea3 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);