Date: Sun, 12 Sep 2010 23:53:11 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Robert Watson <rwatson@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r212506 - head/sys/nfsclient Message-ID: <20100912205311.GG2465@deviant.kiev.zoral.com.ua> In-Reply-To: <alpine.BSF.2.00.1009122140040.52130@fledge.watson.org> References: <201009121906.o8CJ68vQ002600@svn.freebsd.org> <alpine.BSF.2.00.1009122140040.52130@fledge.watson.org>
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--lqtP4FxvQo6hb6bg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Sep 12, 2010 at 09:41:46PM +0100, Robert Watson wrote: >=20 > On Sun, 12 Sep 2010, Konstantin Belousov wrote: >=20 > > Do not fork nfsiod directly from the vop methods. This causes LORs betw= een > > vnode lock and several locks needed during fork, like fd lock. > > > > Instead, schedule the task to be executed in the taskqueue context. We > > still waiting for the fork to finish, but the context of the thread > > executing the task does not make real LORs with our vnode lock. >=20 > Does this actually functionally improve things, or is all this complexity= =20 > about suppressing the lock order reversal? If we're waiting synchronousl= y=20 > for the other thread to launch from the task queue, then the lock order= =20 > reversal still exists, it's just not visible to WITNESS... If we had a= =20 > static analysis tool that could run on lock and sleep/wakeup traces, it= =20 > would still show a deadlock opportunity. As I said in commit message, the deadlock should be fixed, because the taskq thread is executed in the kernel process that should even not have file descriptors at all. --lqtP4FxvQo6hb6bg Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkyNPbYACgkQC3+MBN1Mb4horACdEfBPBECx7PKyITCdgySMJXtg i+8AoMowsZKPz3IJIAjmZin4Ba6dD3YN =Qiid -----END PGP SIGNATURE----- --lqtP4FxvQo6hb6bg--
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