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fix file descriptor locking (from joerg). 

fixes kernel crashes by running go
XXX: pullup-7
This commit is contained in:
christos 2017-07-01 20:08:56 +00:00
parent f36a117b25
commit c4aed00fad
2 changed files with 30 additions and 14 deletions
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31
sys/kern/kern_event.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: kern_event.c,v 1.91 2017/05/11 23:50:17 christos Exp $ */
/* $NetBSD: kern_event.c,v 1.92 2017/07/01 20:08:56 christos Exp $ */
/*-
* Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@ -58,7 +58,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_event.c,v 1.91 2017/05/11 23:50:17 christos Exp $");
__KERNEL_RCSID(0, "$NetBSD: kern_event.c,v 1.92 2017/07/01 20:08:56 christos Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@ -1021,8 +1021,9 @@ kqueue_register(struct kqueue *kq, struct kevent *kev)
if (error != 0) {
#ifdef DIAGNOSTIC
printf("%s: event not supported for file type"
" %d (error %d)\n", __func__, kn->kn_obj ?
printf("%s: event type %d not supported for "
"file type %d (error %d)\n", __func__,
kn->kn_filter, kn->kn_obj ?
((file_t *)kn->kn_obj)->f_type : -1, error);
#endif
/* knote_detach() drops fdp->fd_lock */
@ -1204,10 +1205,19 @@ kqueue_scan(file_t *fp, size_t maxevents, struct kevent *ulistp,
error = 0;
}
}
mutex_spin_exit(&kq->kq_lock);
} else {
/* mark end of knote list */
TAILQ_INSERT_TAIL(&kq->kq_head, marker, kn_tqe);
/*
* Acquire the fdp->fd_lock interlock to avoid races with
* file creation/destruction from other threads.
*/
mutex_spin_exit(&kq->kq_lock);
mutex_enter(&fdp->fd_lock);
mutex_spin_enter(&kq->kq_lock);
while (count != 0) {
kn = TAILQ_FIRST(&kq->kq_head); /* get next knote */
while ((kn->kn_status & KN_MARKER) != 0) {
@ -1218,6 +1228,7 @@ kqueue_scan(file_t *fp, size_t maxevents, struct kevent *ulistp,
(timeout = gettimeleft(&ats,
&sleepts)) <= 0))
goto done;
mutex_exit(&fdp->fd_lock);
goto retry;
}
/* someone else's marker. */
@ -1239,6 +1250,7 @@ kqueue_scan(file_t *fp, size_t maxevents, struct kevent *ulistp,
KASSERT(kn->kn_fop != NULL);
KASSERT(kn->kn_fop->f_event != NULL);
KERNEL_LOCK(1, NULL); /* XXXSMP */
KASSERT(mutex_owned(&fdp->fd_lock));
rv = (*kn->kn_fop->f_event)(kn, 0);
KERNEL_UNLOCK_ONE(NULL); /* XXXSMP */
mutex_spin_enter(&kq->kq_lock);
@ -1261,10 +1273,10 @@ kqueue_scan(file_t *fp, size_t maxevents, struct kevent *ulistp,
nkev++;
if (kn->kn_flags & EV_ONESHOT) {
/* delete ONESHOT events after retrieval */
mutex_spin_exit(&kq->kq_lock);
mutex_enter(&fdp->fd_lock);
kn->kn_status &= ~KN_BUSY;
mutex_spin_exit(&kq->kq_lock);
knote_detach(kn, fdp, true);
mutex_enter(&fdp->fd_lock);
mutex_spin_enter(&kq->kq_lock);
} else if (kn->kn_flags & EV_CLEAR) {
/* clear state after retrieval */
@ -1286,9 +1298,11 @@ kqueue_scan(file_t *fp, size_t maxevents, struct kevent *ulistp,
if (nkev == kevcnt) {
/* do copyouts in kevcnt chunks */
mutex_spin_exit(&kq->kq_lock);
mutex_exit(&fdp->fd_lock);
error = (*keops->keo_put_events)
(keops->keo_private,
kevbuf, ulistp, nevents, nkev);
mutex_enter(&fdp->fd_lock);
mutex_spin_enter(&kq->kq_lock);
nevents += nkev;
nkev = 0;
@ -1301,9 +1315,10 @@ kqueue_scan(file_t *fp, size_t maxevents, struct kevent *ulistp,
break;
}
}
}
done:
mutex_spin_exit(&kq->kq_lock);
mutex_spin_exit(&kq->kq_lock);
mutex_exit(&fdp->fd_lock);
}
if (nkev != 0) {
/* copyout remaining events */
error = (*keops->keo_put_events)(keops->keo_private,

13
sys/sys/event.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: event.h,v 1.29 2017/06/14 16:37:05 christos Exp $ */
/* $NetBSD: event.h,v 1.30 2017/07/01 20:08:56 christos Exp $ */
/*-
* Copyright (c) 1999,2000,2001 Jonathan Lemon <jlemon@FreeBSD.org>
@ -188,10 +188,10 @@ struct knote {
TAILQ_ENTRY(knote) kn_tqe; /* q: for struct kqueue */
struct kqueue *kn_kq; /* q: which queue we are on */
struct kevent kn_kevent;
uint32_t kn_status;
uint32_t kn_sfflags; /* saved filter flags */
uintptr_t kn_sdata; /* saved data field */
void *kn_obj; /* pointer to monitored obj */
uint32_t kn_status; /* q: flags below */
uint32_t kn_sfflags; /* saved filter flags */
uintptr_t kn_sdata; /* saved data field */
void *kn_obj; /* monitored obj */
const struct filterops *kn_fop;
struct kfilter *kn_kfilter;
void *kn_hook;
@ -201,7 +201,8 @@ struct knote {
#define KN_DISABLED 0x04U /* event is disabled */
#define KN_DETACHED 0x08U /* knote is detached */
#define KN_MARKER 0x10U /* is a marker */
#define KN_BUSY 0x20U /* is being scanned */
#define KN_BUSY 0x20U /* is being scanned */
/* Toggling KN_BUSY also requires kn_kq->kq_fdp->fd_lock. */
#define kn_id kn_kevent.ident
#define kn_filter kn_kevent.filter