Date: Fri, 19 Oct 2007 15:10:02 GMT From: John Baldwin <jhb@FreeBSD.org> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/89538: [tty] [panic] triggered by "sysctl -a" Message-ID: <200710191510.l9JFA2RM049934@freefall.freebsd.org>
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The following reply was made to PR kern/89538; it has been noted by GNATS.
From: John Baldwin <jhb@freebsd.org>
To: bug-followup@freebsd.org,
gkozyrev@gmail.com
Cc:
Subject: Re: kern/89538: [tty] [panic] triggered by "sysctl -a"
Date: Fri, 19 Oct 2007 10:44:40 -0400
One thing I noted is that si_usecount is -1 in the most recent gdb output.
One possible race is that we read vp->v_usecount w/o holding the vnode
interlock in devfs_reclaim(), so perhaps there is a race between
VOP_RECLAIM() and some other thread doing a vref() such that the
cdev is prematurely freed? Patch is below:
--- //depot/user/jhb/acpipci/fs/devfs/devfs_vnops.c
+++ /home/john/work/p4/acpipci/fs/devfs/devfs_vnops.c
@@ -995,17 +995,20 @@
vnode_destroy_vobject(vp);
+ VI_LOCK(vp);
dev_lock();
dev = vp->v_rdev;
vp->v_rdev = NULL;
if (dev == NULL) {
dev_unlock();
+ VI_UNLOCK(vp);
return (0);
}
dev->si_usecount -= vp->v_usecount;
dev_unlock();
+ VI_UNLOCK(vp);
dev_rel(dev);
return (0);
}
--
John Baldwin
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