Date: Tue, 8 Oct 2002 22:46:05 +0200 From: Stefan Farfeleder <e0026813@stud3.tuwien.ac.at> To: Terry Lambert <tlambert2@mindspring.com> Cc: John Baldwin <jhb@FreeBSD.ORG>, Juli Mallett <jmallett@FreeBSD.ORG>, current@FreeBSD.ORG Subject: Re: [PATCH] Re: Junior Kernel Hacker page updated... Message-ID: <20021008204605.GA252@frog.fafoe> In-Reply-To: <3DA1668D.E8153F43@mindspring.com> References: <20021004132203.A78223@FreeBSD.org> <XFMail.20021004163317.jhb@FreeBSD.org> <20021005135504.GA254@frog.fafoe> <3D9F39BB.66126C35@mindspring.com> <3DA12642.28BB8E1@mindspring.com> <20021007095024.GA252@frog.fafoe> <3DA1668D.E8153F43@mindspring.com>
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On Mon, Oct 07, 2002 at 03:48:45AM -0700, Terry Lambert wrote:
>
> *** OK, it's very hard to believe you didn't break into the
> *** debugger and manually call "pnaic" to get this to happen.
You're right, this is exactly what I did.
> I can't personally repeat the problem, so you're elected to do
> the legwork on this one. 8-(.
Following the advice from the spl* man page I turned the spl* calls to a
mutex and was surprised to see it working. My SMP -current survived a 'make
-j16 buildworld' with make using kqueue() (which it did not a single
time out of >30 times before). Further testings will follow tomorrow.
However, WITNESS complains (only once) about this:
lock order reversal
1st 0xc662140c kqueue mutex (kqueue mutex) @ /freebsd/current/src/sys/kern/kern_event.c:714
2nd 0xc6727d00 pipe mutex (pipe mutex) @ /freebsd/current/src/sys/kern/sys_pipe.c:1478
Regards,
Stefan Farfeleder
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Index: sys/eventvar.h
===================================================================
RCS file: /home/ncvs/src/sys/sys/eventvar.h,v
retrieving revision 1.4
diff -u -r1.4 eventvar.h
--- sys/eventvar.h 18 Jul 2000 19:31:48 -0000 1.4
+++ sys/eventvar.h 8 Oct 2002 16:06:46 -0000
@@ -35,6 +35,7 @@
struct kqueue {
TAILQ_HEAD(kqlist, knote) kq_head; /* list of pending event */
int kq_count; /* number of pending events */
+ struct mtx kq_mtx; /* protect kq_head */
struct selinfo kq_sel;
struct filedesc *kq_fdp;
int kq_state;
Index: kern/kern_event.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_event.c,v
retrieving revision 1.46
diff -u -r1.46 kern_event.c
--- kern/kern_event.c 3 Oct 2002 06:03:26 -0000 1.46
+++ kern/kern_event.c 8 Oct 2002 19:22:27 -0000
@@ -375,7 +375,7 @@
if (error)
goto done2;
kq = malloc(sizeof(struct kqueue), M_KQUEUE, M_WAITOK | M_ZERO);
- TAILQ_INIT(&kq->kq_head);
+ mtx_init(&kq->kq_mtx, "kqueue mutex", NULL, MTX_DEF);
FILE_LOCK(fp);
fp->f_flag = FREAD | FWRITE;
fp->f_type = DTYPE_KQUEUE;
@@ -709,13 +709,15 @@
error = 0;
goto done;
}
+ splx(s);
+ mtx_lock(&kq->kq_mtx);
TAILQ_INSERT_TAIL(&kq->kq_head, &marker, kn_tqe);
while (count) {
kn = TAILQ_FIRST(&kq->kq_head);
TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
if (kn == &marker) {
- splx(s);
+ mtx_unlock(&kq->kq_mtx);
if (count == maxevents)
goto retry;
goto done;
@@ -737,10 +739,10 @@
if (kn->kn_flags & EV_ONESHOT) {
kn->kn_status &= ~KN_QUEUED;
kq->kq_count--;
- splx(s);
+ mtx_unlock(&kq->kq_mtx);
kn->kn_fop->f_detach(kn);
knote_drop(kn, td);
- s = splhigh();
+ mtx_lock(&kq->kq_mtx);
} else if (kn->kn_flags & EV_CLEAR) {
kn->kn_data = 0;
kn->kn_fflags = 0;
@@ -751,19 +753,19 @@
}
count--;
if (nkev == KQ_NEVENTS) {
- splx(s);
+ mtx_unlock(&kq->kq_mtx);
error = copyout(&kq->kq_kev, ulistp,
sizeof(struct kevent) * nkev);
ulistp += nkev;
nkev = 0;
kevp = kq->kq_kev;
- s = splhigh();
+ mtx_lock(&kq->kq_mtx);
if (error)
break;
}
}
TAILQ_REMOVE(&kq->kq_head, &marker, kn_tqe);
- splx(s);
+ mtx_unlock(&kq->kq_mtx);
done:
if (nkev != 0)
error = copyout(&kq->kq_kev, ulistp,
@@ -887,6 +889,7 @@
}
}
FILEDESC_UNLOCK(fdp);
+ mtx_destroy(&kq->kq_mtx);
free(kq, M_KQUEUE);
fp->f_data = NULL;
@@ -1051,14 +1054,14 @@
knote_enqueue(struct knote *kn)
{
struct kqueue *kq = kn->kn_kq;
- int s = splhigh();
KASSERT((kn->kn_status & KN_QUEUED) == 0, ("knote already queued"));
+ mtx_lock(&kq->kq_mtx);
TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
kn->kn_status |= KN_QUEUED;
kq->kq_count++;
- splx(s);
+ mtx_unlock(&kq->kq_mtx);
kqueue_wakeup(kq);
}
@@ -1066,14 +1069,14 @@
knote_dequeue(struct knote *kn)
{
struct kqueue *kq = kn->kn_kq;
- int s = splhigh();
KASSERT(kn->kn_status & KN_QUEUED, ("knote not queued"));
+ mtx_lock(&kq->kq_mtx);
TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
kn->kn_status &= ~KN_QUEUED;
kq->kq_count--;
- splx(s);
+ mtx_unlock(&kq->kq_mtx);
}
static void
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