Date: Fri, 5 Dec 2008 23:03:49 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Julian Elischer <julian@elischer.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r185647 - in head/sys: kern sys Message-ID: <20081205210349.GQ2038@deviant.kiev.zoral.com.ua> In-Reply-To: <49399510.2030104@elischer.org> References: <200812052050.mB5KoOcV072648@svn.freebsd.org> <49399510.2030104@elischer.org>
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--H2kTGx6mr3R59oXC Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Dec 05, 2008 at 12:54:40PM -0800, Julian Elischer wrote: > Konstantin Belousov wrote: > >Author: kib > >Date: Fri Dec 5 20:50:24 2008 > >New Revision: 185647 > >URL: http://svn.freebsd.org/changeset/base/185647 > > > >Log: > > Several threads in a process may do vfork() simultaneously. Then, all > > parent threads sleep on the parent' struct proc until corresponding > > child releases the vmspace. Each sleep is interlocked with proc mutex = of > > the child, that triggers assertion in the sleepq_add(). The assertion > > requires that at any time, all simultaneous sleepers for the channel u= se > > the same interlock. >=20 > We DID have a thread_single() in the fork code so that > only one thread would proceed through the fork itself at a time. > However it was removed last year as it proved to be a problem in some=20 > cases. Maybe we need to look at replacing it in some way. Yes, I know, and I considered restoring conditional single-threading for the vfork(). But it would immediately bring back all NFS client problems, associated with this (at least sleeping with vnode lock held and nfsbiod creation deadlocks). This is a second problem caused by removal of the single-threading. Nonetheless, I think that your change was right, and we shall just fix a corner cases. --H2kTGx6mr3R59oXC Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkk5lzQACgkQC3+MBN1Mb4jDrwCfSHI2WPu10vxN2JOd4DKcCCvI P9IAnjw6MosZ2AjszKnkkv/TER0JlOwi =jl/g -----END PGP SIGNATURE----- --H2kTGx6mr3R59oXC--
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