Date: Thu, 8 Dec 2005 09:56:35 -0500 From: John Baldwin <jhb@freebsd.org> To: Craig Rodrigues <rodrigc@crodrigues.org> Cc: freebsd-arch@freebsd.org Subject: Re: [RFC] Implement cv_wait_nolock(), for emulation of SGI's sv_wait() Message-ID: <200512080956.36425.jhb@freebsd.org> In-Reply-To: <20051207224359.GA4320@crodrigues.org> References: <20051207224359.GA4320@crodrigues.org>
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On Wednesday 07 December 2005 05:43 pm, Craig Rodrigues wrote: > Hi, > > As part of the XFS for FreeBSD project, Alexander Kabaev > implemented a cv_wait_nolock() function for compatibility > with SGI's sv_wait() call: > http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?coll=0650&db=man&fna >me=/usr/share/catman/p_man/catD/SV_WAIT.z > > sv_wait() waits on a synchronization variable, the lock must be held > before the call is entered, but the lock is not held when sv_wait() is > exited. > > Is this patch OK to go into FreeBSD? > Comments? As I said on IRC, I'm not a big fan of this or PDROP, but PDROP is in the tree. Note that you could implement sv_wait() using the existing primitives via: sv_wait() { cv_wait() mtx_unlock() } If you do stick with cv_wait_nolock(), _please_ don't duplicate a whole bunch of code by implement cv_wait() like so: cv_wait() { cv_wait_nolock() mtx_lock() } Note that currently you have a bug in the cold || panicstr case in that the function doesn't drop the lock. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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