The branch main has been updated by kib:
URL:
https://cgit.FreeBSD.org/src/commit/?id=2ce23b1f76721e44646fc98ba4e24a113a6d5972
commit 2ce23b1f76721e44646fc98ba4e24a113a6d5972
Author: Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2024-03-06 07:24:22 +0000
Commit: Konstantin Belousov <k...@freebsd.org>
CommitDate: 2024-03-06 07:25:14 +0000
libc posix_spawn(): explain why rtld can be used after fork
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
---
lib/libc/gen/posix_spawn.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/lib/libc/gen/posix_spawn.c b/lib/libc/gen/posix_spawn.c
index d405517ba68d..ee2ce05ff317 100644
--- a/lib/libc/gen/posix_spawn.c
+++ b/lib/libc/gen/posix_spawn.c
@@ -325,6 +325,11 @@ do_posix_spawn(pid_t *pid, const char *path,
* ideal vfork(2) if we get an EINVAL from rfork -- this should only
* happen with newer libc on older kernel that doesn't accept
* RFSPAWN.
+ *
+ * Combination of vfork() (or its equivalent rfork() form) and
+ * a special property of the libthr rtld locks ensure that
+ * rtld is operational in the child. In particular, libthr
+ * rtld locks do not store owner' tid into the lock word.
*/
#ifdef _RFORK_THREAD_STACK_SIZE
/*
