Date: Wed, 26 Sep 2012 07:52:04 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Ed Maste <emaste@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r240938 - head/sys/net Message-ID: <20120926045204.GG35915@deviant.kiev.zoral.com.ua> In-Reply-To: <201209252210.q8PMAEx5003950@svn.freebsd.org> References: <201209252210.q8PMAEx5003950@svn.freebsd.org>
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[-- Attachment #1 --] On Tue, Sep 25, 2012 at 10:10:14PM +0000, Ed Maste wrote: > Author: emaste > Date: Tue Sep 25 22:10:14 2012 > New Revision: 240938 > URL: http://svn.freebsd.org/changeset/base/240938 > > Log: > Avoid INVARIANTS panic destroying an in-use tap(4) > > The requirement (implied by the KASSERT in tap_destroy) that the tap is > closed isn't valid; destroy_dev will block in devdrn while other threads > are in d_* functions. Are you sure ? The device may be opened, but no threads could be in any cdevsw methods. destroy_dev(9) only waits for threads to leave cdevsw methods, and not for the close to happen. This is normal situation, but driver shall be aware of it and handle it properly. > > Note: if_tun had the same issue, addressed in SVN revisions r186391, > r186483 and r186497. The use of the condvar there appears to be > redundant with the functionality provided by destroy_dev. > > Sponsored by: ADARA Networks > Reviewed by: dwhite > MFC after: 2 weeks > > Modified: > head/sys/net/if_tap.c > head/sys/net/if_tapvar.h > > Modified: head/sys/net/if_tap.c > ============================================================================== > --- head/sys/net/if_tap.c Tue Sep 25 21:33:36 2012 (r240937) > +++ head/sys/net/if_tap.c Tue Sep 25 22:10:14 2012 (r240938) > @@ -213,14 +213,10 @@ tap_destroy(struct tap_softc *tp) > { > struct ifnet *ifp = tp->tap_ifp; > > - /* Unlocked read. */ > - KASSERT(!(tp->tap_flags & TAP_OPEN), > - ("%s flags is out of sync", ifp->if_xname)); > - > CURVNET_SET(ifp->if_vnet); > + destroy_dev(tp->tap_dev); > seldrain(&tp->tap_rsel); > knlist_destroy(&tp->tap_rsel.si_note); > - destroy_dev(tp->tap_dev); > ether_ifdetach(ifp); > if_free(ifp); > > > Modified: head/sys/net/if_tapvar.h > ============================================================================== > --- head/sys/net/if_tapvar.h Tue Sep 25 21:33:36 2012 (r240937) > +++ head/sys/net/if_tapvar.h Tue Sep 25 22:10:14 2012 (r240938) > @@ -64,6 +64,7 @@ struct tap_softc { > SLIST_ENTRY(tap_softc) tap_next; /* next device in chain */ > struct cdev *tap_dev; > struct mtx tap_mtx; /* per-softc mutex */ > + struct cv tap_cv; /* protect ref'd dev destroy */ > }; > > #endif /* !_NET_IF_TAPVAR_H_ */ [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAlBiifQACgkQC3+MBN1Mb4h2vQCfRZkdCRvUiAtluuB+UzbYfZgv 1h8An0bkf+q1VEsLaKDgaIHa7MbygL4A =Vbpb -----END PGP SIGNATURE-----
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