Here is another attempt to set klist lock for sockets. This is a revised version of a patch that I posted in January [1].
Using solock() for the klists is probably the easiest way at the time being. However, the lock is a potential point of contention because of the underlying big-lock design. The increase of overhead is related to adding and removing event registrations. With persistent registrations the overhead is unchanged. As a result, socket and named FIFO event filters should be ready to run without the kernel lock. The f_event, f_modify and f_process callbacks should be MP-safe already. [1] https://marc.info/?l=openbsd-tech&m=160986578724696 OK? Index: kern/uipc_socket.c =================================================================== RCS file: src/sys/kern/uipc_socket.c,v retrieving revision 1.265 diff -u -p -r1.265 uipc_socket.c --- kern/uipc_socket.c 14 Oct 2021 23:05:10 -0000 1.265 +++ kern/uipc_socket.c 22 Oct 2021 12:17:57 -0000 @@ -84,7 +84,7 @@ int filt_solistenprocess(struct knote *k int filt_solisten_common(struct knote *kn, struct socket *so); const struct filterops solisten_filtops = { - .f_flags = FILTEROP_ISFD, + .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, .f_attach = NULL, .f_detach = filt_sordetach, .f_event = filt_solisten, @@ -93,7 +93,7 @@ const struct filterops solisten_filtops }; const struct filterops soread_filtops = { - .f_flags = FILTEROP_ISFD, + .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, .f_attach = NULL, .f_detach = filt_sordetach, .f_event = filt_soread, @@ -102,7 +102,7 @@ const struct filterops soread_filtops = }; const struct filterops sowrite_filtops = { - .f_flags = FILTEROP_ISFD, + .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, .f_attach = NULL, .f_detach = filt_sowdetach, .f_event = filt_sowrite, @@ -111,7 +111,7 @@ const struct filterops sowrite_filtops = }; const struct filterops soexcept_filtops = { - .f_flags = FILTEROP_ISFD, + .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, .f_attach = NULL, .f_detach = filt_sordetach, .f_event = filt_soread, @@ -169,6 +169,8 @@ socreate(int dom, struct socket **aso, i return (EPROTOTYPE); so = pool_get(&socket_pool, PR_WAITOK | PR_ZERO); rw_init(&so->so_lock, "solock"); + klist_init(&so->so_rcv.sb_sel.si_note, &socket_klistops, so); + klist_init(&so->so_snd.sb_sel.si_note, &socket_klistops, so); sigio_init(&so->so_sigio); TAILQ_INIT(&so->so_q0); TAILQ_INIT(&so->so_q); @@ -258,6 +260,8 @@ sofree(struct socket *so, int s) } } sigio_free(&so->so_sigio); + klist_free(&so->so_rcv.sb_sel.si_note); + klist_free(&so->so_snd.sb_sel.si_note); #ifdef SOCKET_SPLICE if (so->so_sp) { if (issplicedback(so)) { @@ -2038,9 +2042,9 @@ soo_kqfilter(struct file *fp, struct kno { struct socket *so = kn->kn_fp->f_data; struct sockbuf *sb; + int s; - KERNEL_ASSERT_LOCKED(); - + s = solock(so); switch (kn->kn_filter) { case EVFILT_READ: if (so->so_options & SO_ACCEPTCONN) @@ -2058,10 +2062,12 @@ soo_kqfilter(struct file *fp, struct kno sb = &so->so_rcv; break; default: + sounlock(so, s); return (EINVAL); } klist_insert_locked(&sb->sb_sel.si_note, kn); + sounlock(so, s); return (0); } @@ -2071,9 +2077,7 @@ filt_sordetach(struct knote *kn) { struct socket *so = kn->kn_fp->f_data; - KERNEL_ASSERT_LOCKED(); - - klist_remove_locked(&so->so_rcv.sb_sel.si_note, kn); + klist_remove(&so->so_rcv.sb_sel.si_note, kn); } int @@ -2159,9 +2163,7 @@ filt_sowdetach(struct knote *kn) { struct socket *so = kn->kn_fp->f_data; - KERNEL_ASSERT_LOCKED(); - - klist_remove_locked(&so->so_snd.sb_sel.si_note, kn); + klist_remove(&so->so_snd.sb_sel.si_note, kn); } int @@ -2284,6 +2286,36 @@ filt_solistenprocess(struct knote *kn, s return (rv); } +void +klist_soassertlk(void *arg) +{ + struct socket *so = arg; + + soassertlocked(so); +} + +int +klist_solock(void *arg) +{ + struct socket *so = arg; + + return (solock(so)); +} + +void +klist_sounlock(void *arg, int ls) +{ + struct socket *so = arg; + + sounlock(so, ls); +} + +const struct klistops socket_klistops = { + .klo_assertlk = klist_soassertlk, + .klo_lock = klist_solock, + .klo_unlock = klist_sounlock, +}; + #ifdef DDB void sobuf_print(struct sockbuf *, Index: kern/uipc_socket2.c =================================================================== RCS file: src/sys/kern/uipc_socket2.c,v retrieving revision 1.113 diff -u -p -r1.113 uipc_socket2.c --- kern/uipc_socket2.c 26 Jul 2021 05:51:13 -0000 1.113 +++ kern/uipc_socket2.c 22 Oct 2021 12:17:57 -0000 @@ -189,6 +189,8 @@ sonewconn(struct socket *head, int conns so->so_rcv.sb_lowat = head->so_rcv.sb_lowat; so->so_rcv.sb_timeo_nsecs = head->so_rcv.sb_timeo_nsecs; + klist_init(&so->so_rcv.sb_sel.si_note, &socket_klistops, so); + klist_init(&so->so_snd.sb_sel.si_note, &socket_klistops, so); sigio_init(&so->so_sigio); sigio_copy(&so->so_sigio, &head->so_sigio); @@ -196,6 +198,8 @@ sonewconn(struct socket *head, int conns if ((*so->so_proto->pr_attach)(so, 0)) { (void) soqremque(so, soqueue); sigio_free(&so->so_sigio); + klist_free(&so->so_rcv.sb_sel.si_note); + klist_free(&so->so_snd.sb_sel.si_note); pool_put(&socket_pool, so); return (NULL); } Index: miscfs/fifofs/fifo_vnops.c =================================================================== RCS file: src/sys/miscfs/fifofs/fifo_vnops.c,v retrieving revision 1.82 diff -u -p -r1.82 fifo_vnops.c --- miscfs/fifofs/fifo_vnops.c 15 Oct 2021 06:30:06 -0000 1.82 +++ miscfs/fifofs/fifo_vnops.c 22 Oct 2021 12:17:57 -0000 @@ -114,7 +114,7 @@ int filt_fifowriteprocess(struct knote * int filt_fifowrite_common(struct knote *kn, struct socket *so); const struct filterops fiforead_filtops = { - .f_flags = FILTEROP_ISFD, + .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, .f_attach = NULL, .f_detach = filt_fifordetach, .f_event = filt_fiforead, @@ -123,7 +123,7 @@ const struct filterops fiforead_filtops }; const struct filterops fifowrite_filtops = { - .f_flags = FILTEROP_ISFD, + .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, .f_attach = NULL, .f_detach = filt_fifowdetach, .f_event = filt_fifowrite, @@ -528,7 +528,7 @@ fifo_kqfilter(void *v) ap->a_kn->kn_hook = so; - klist_insert_locked(&sb->sb_sel.si_note, ap->a_kn); + klist_insert(&sb->sb_sel.si_note, ap->a_kn); return (0); } @@ -538,7 +538,7 @@ filt_fifordetach(struct knote *kn) { struct socket *so = (struct socket *)kn->kn_hook; - klist_remove_locked(&so->so_rcv.sb_sel.si_note, kn); + klist_remove(&so->so_rcv.sb_sel.si_note, kn); } int @@ -609,7 +609,7 @@ filt_fifowdetach(struct knote *kn) { struct socket *so = (struct socket *)kn->kn_hook; - klist_remove_locked(&so->so_snd.sb_sel.si_note, kn); + klist_remove(&so->so_snd.sb_sel.si_note, kn); } int Index: sys/event.h =================================================================== RCS file: src/sys/sys/event.h,v retrieving revision 1.56 diff -u -p -r1.56 event.h --- sys/event.h 16 Jun 2021 14:26:30 -0000 1.56 +++ sys/event.h 22 Oct 2021 12:17:57 -0000 @@ -285,6 +285,7 @@ struct timespec; extern const struct filterops sig_filtops; extern const struct filterops dead_filtops; +extern const struct klistops socket_klistops; extern void kqpoll_init(void); extern void kqpoll_exit(void);
