- Improve BPF locking model.

Interface locks and descriptor locks are converted from mutex(9) to rwlock(9).
This greately improves performance: in most common case we need to acquire 1
reader lock instead of 2 mutexes.

- Remove filter(descriptor) (reader) lock in bpf_mtap[2]
This was suggested by glebius@. We protect filter by requesting interface
writer lock on filter change.

- Cover struct bpf_if under BPF_INTERNAL define. This permits including bpf.h
without including rwlock stuff. However, this is is temporary solution,
struct bpf_if should be made opaque for any external caller.

Found by:       Dmitrij Tejblum <tejblum@yandex-team.ru>
Sponsored by:   Yandex LLC

Reviewed by:    glebius (previous version)
Reviewed by:    silence on -net@
Approved by:    (mentor)

MFC after:      3 weeks

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index bd2a5cb..52045b6 100644
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -563,8 +563,8 @@ static struct witness_order_list_entry order_lists[] = {
 	 * BPF
 	 */
 	{ "bpf global lock", &lock_class_mtx_sleep },
-	{ "bpf interface lock", &lock_class_mtx_sleep },
-	{ "bpf cdev lock", &lock_class_mtx_sleep },
+	{ "bpf interface lock", &lock_class_rw },
+	{ "bpf cdev lock", &lock_class_rw },
 	{ NULL, NULL },
 	/*
 	 * NFS server