Date: Wed, 2 Jan 2008 12:17:21 -0500 From: John Baldwin <jhb@freebsd.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: rrs@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org, brde@optusnet.com.au, cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/netinet sctp_bsd_addr.c Message-ID: <200801021217.22195.jhb@freebsd.org> In-Reply-To: <20080101.024546.1079618522.imp@bsdimp.com> References: <200712311219.08286.jhb@freebsd.org> <20080101161858.A10345@delplex.bde.org> <20080101.024546.1079618522.imp@bsdimp.com>
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On Tuesday 01 January 2008 04:45:46 am M. Warner Losh wrote: > In message: <20080101161858.A10345@delplex.bde.org> > Bruce Evans <brde@optusnet.com.au> writes: > : On Mon, 31 Dec 2007, M. Warner Losh wrote: > : > : > In message: <200712311219.08286.jhb@freebsd.org> > : > John Baldwin <jhb@FreeBSD.org> writes: > : > : > : The more correct fix though is to do a 'sched_prio()' at the start of the > : > : thread's main loop to set the priority and then not adjust it via msleep(). > : > : Kernel threads really should never pass a priority to msleep() but always '0' > : > : (which means "don't change my priority"). > : > > : > Not PZERO? When should one use PZERO and when should one use a bare > : > '0'? Can this information be added to the man page? > : > : PZERO is compatibility cruft which should never be used. Just a few > : places in kern still use it to invent a priority when no suitable > : priority (like PSOCK or PRIBIO) is already #defined. It isn't clear > : where these invented priorities are suitable. > > Do we want to document the other Pxxxx priorities? Also, PZERO is meant to be a base for userland priorities (threads in userland should be <= PZERO except for real time threads) and is an actual priority value. 0 means "don't change anything." > : Otherwise, PZERO has a completely different meaning from either priority > : 0 (maximal) or the bare 0 arg to msleep. It means some middle priority, > : or the bias from priority 0 to get to that middle priority, so that > : after subtracting it, 0 becomes the middle priority. The bare 0 is > : actualy priority 0 (maximal) overloaded to mean "don't change the > : priority". This overloading doesn't lose anything except clarity since > : nothing is permitted to wake up at maximal priority after a sleep. > : (Maximal priority is reserved for realtime priority ithreads and even > : much lower priority ithreads are not permitted to sleep, and non-interrupt > : threads aren't permitted to run at ithread priorities except temporarily > : for priority propagation.) > > So would the following be a reasonable change to sleep.9? > > Index: sleep.9 > =================================================================== > RCS file: /home/ncvs/src/share/man/man9/sleep.9,v > retrieving revision 1.61 > diff -u -r1.61 sleep.9 > --- sleep.9 30 Mar 2007 18:07:26 -0000 1.61 > +++ sleep.9 1 Jan 2008 09:44:01 -0000 > @@ -93,6 +93,10 @@ > runnable with the specified > .Fa priority > when it resumes. > +.Dv PZERO > +should never be used, as it is for compatibility only. > +A new priority of 0 means to use the thread's current priority when > +it is made runnable again. > If > .Fa priority > includes the The manpage already says that priority 0 doesn't change the priority (look at the first half of the sentence before your new one). I'm not sure PZERO deserves special mention. You could perhaps add a new section after 'DESCRIPTION' that covers the various Pxxx priorities that are often used for *sleep() routines such as PZERO, PSOCK, PVM, etc. -- John Baldwin
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