Date: Sat, 6 Dec 2008 01:00:02 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Roman Divacky <rdivacky@freebsd.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: <20081205230002.GX2038@deviant.kiev.zoral.com.ua> In-Reply-To: <20081205224600.GA16948@freebsd.org> References: <200812052050.mB5KoOcV072648@svn.freebsd.org> <20081205224600.GA16948@freebsd.org>
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--tgO4DUqb0GCKXXLG Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Dec 05, 2008 at 11:46:00PM +0100, Roman Divacky wrote: > On Fri, Dec 05, 2008 at 08:50:24PM +0000, Konstantin Belousov wrote: > > Author: kib > > Date: Fri Dec 5 20:50:24 2008 > > New Revision: 185647 > > URL: http://svn.freebsd.org/changeset/base/185647 > >=20 > > 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 = use > > the same interlock. > > =20 > > Silent the assertion by using conditional variable allocated in the > > child. Broadcast the variable event on exec() and exit(). > > =20 > > Since struct proc * sleep wait channel is overloaded for several > > unrelated events, I was unable to remove wakeups from the places where > > cv_broadcast() is added, except exec(). >=20 > are there any differences (performance etc.) in using condition variables > instead of sleep/wakeup? I do not think that there is any measurable difference. On the other hand, the patch makes struct proc bigger by int + pointer. This shall not be a problem too. Would I been able to convert _all_ uses of the struct proc * wait channel to cond vars operation, this may be measurable on some loads, since it would exclude spurious wakeups. --tgO4DUqb0GCKXXLG Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkk5snIACgkQC3+MBN1Mb4jlrgCeOSR6qYzMOOnwNAJPHrBIt81D xFoAoLdHTMa7kmqMzcVYBIvLWVlUCi/j =97eS -----END PGP SIGNATURE----- --tgO4DUqb0GCKXXLG--
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