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Date:      Wed, 26 Sep 2012 10:56:15 +0400
From:      Gleb Smirnoff <glebius@FreeBSD.org>
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:  <20120926065615.GZ50433@FreeBSD.org>
In-Reply-To: <201209252210.q8PMAEx5003950@svn.freebsd.org>
References:  <201209252210.q8PMAEx5003950@svn.freebsd.org>
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  Ed,

On Tue, Sep 25, 2012 at 10:10:14PM +0000, Ed Maste wrote:
E> Author: emaste
E> Date: Tue Sep 25 22:10:14 2012
E> New Revision: 240938
E> URL: http://svn.freebsd.org/changeset/base/240938
E> 
E> Log:
E>   Avoid INVARIANTS panic destroying an in-use tap(4)
E>   
E>   The requirement (implied by the KASSERT in tap_destroy) that the tap is
E>   closed isn't valid; destroy_dev will block in devdrn while other threads
E>   are in d_* functions.
E>   
E>   Note: if_tun had the same issue, addressed in SVN revisions r186391,
E>   r186483 and r186497.  The use of the condvar there appears to be
E>   redundant with the functionality provided by destroy_dev.

So why did you add condvar to the softc? See it in diff below.

E>   Sponsored by:	ADARA Networks
E>   Reviewed by:	dwhite
E>   MFC after:	2 weeks
E> 
E> Modified:
E>   head/sys/net/if_tap.c
E>   head/sys/net/if_tapvar.h
E> 
E> Modified: head/sys/net/if_tap.c
E> ==============================================================================
E> --- head/sys/net/if_tap.c	Tue Sep 25 21:33:36 2012	(r240937)
E> +++ head/sys/net/if_tap.c	Tue Sep 25 22:10:14 2012	(r240938)
E> @@ -213,14 +213,10 @@ tap_destroy(struct tap_softc *tp)
E>  {
E>  	struct ifnet *ifp = tp->tap_ifp;
E>  
E> -	/* Unlocked read. */
E> -	KASSERT(!(tp->tap_flags & TAP_OPEN),
E> -		("%s flags is out of sync", ifp->if_xname));
E> -
E>  	CURVNET_SET(ifp->if_vnet);
E> +	destroy_dev(tp->tap_dev);
E>  	seldrain(&tp->tap_rsel);
E>  	knlist_destroy(&tp->tap_rsel.si_note);
E> -	destroy_dev(tp->tap_dev);
E>  	ether_ifdetach(ifp);
E>  	if_free(ifp);
E>  
E> 
E> Modified: head/sys/net/if_tapvar.h
E> ==============================================================================
E> --- head/sys/net/if_tapvar.h	Tue Sep 25 21:33:36 2012	(r240937)
E> +++ head/sys/net/if_tapvar.h	Tue Sep 25 22:10:14 2012	(r240938)
E> @@ -64,6 +64,7 @@ struct tap_softc {
E>  	SLIST_ENTRY(tap_softc)	tap_next;	/* next device in chain      */
E>  	struct cdev *tap_dev;
E>  	struct mtx	 tap_mtx;		/* per-softc mutex */
E> +	struct cv	 tap_cv;		/* protect ref'd dev destroy */ 
E>  };
E>  
E>  #endif /* !_NET_IF_TAPVAR_H_ */

-- 
Totus tuus, Glebius.

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