Date: Wed, 23 Mar 2011 11:25:47 -0400 From: John Baldwin <jhb@freebsd.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: svn-src-head@freebsd.org, Edward Tomasz Napierala <trasz@freebsd.org>, svn-src-all@freebsd.org, src-committers@freebsd.org, Julian Elischer <julian@freebsd.org> Subject: Re: svn commit: r219727 - head/sys/vm Message-ID: <201103231125.48082.jhb@freebsd.org> In-Reply-To: <20110323143434.GZ78089@deviant.kiev.zoral.com.ua> References: <201103180647.p2I6lNCB051745@svn.freebsd.org> <201103230945.37726.jhb@freebsd.org> <20110323143434.GZ78089@deviant.kiev.zoral.com.ua>
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On Wednesday, March 23, 2011 10:34:34 am Kostik Belousov wrote: > On Wed, Mar 23, 2011 at 09:45:37AM -0400, John Baldwin wrote: > > On Friday, March 18, 2011 4:40:34 am Julian Elischer wrote: > > > On 3/17/11 11:47 PM, Edward Tomasz Napierala wrote: > > > > Author: trasz > > > > Date: Fri Mar 18 06:47:23 2011 > > > > New Revision: 219727 > > > > URL: http://svn.freebsd.org/changeset/base/219727 > > > > > > > > Log: > > > > In vm_daemon(), when iterating over all processes in the system, skip those > > > > which are not yet fully initialized (i.e. ones with p_state == PRS_NEW). > > > > Without it, we could panic in _thread_lock_flags(). > > > > > > > > Note that there may be other instances of FOREACH_PROC_IN_SYSTEM() that > > > > require similar fix. > > > > > > In the past each process was only put on the process list after it was > > > fully set up. > > > Did someone change that recently? that would be "A Bad Thing" (TM). > > > > Err, no, that has never been true. The reason it has to go on the list > > immediately is to reserve the PID against concurrent fork()s. > > > > Hmm, the locking of prs_state is a bit busted it seems. Both the PROC_LOCK() > > and PROC_SLOCK() are supposed to be held when it is written to, but > > PROC_LOCK() is missing in fork1() when moving the state to PRS_NORMAL. > > > > Also, this commit should check against PRS_NORMAL after acquiring the proc > > lock, not before. > In the case of this commit, it does not matter much, I think. The reason > is that all the check want is to make sure that there is at least one > fully initialized thread linked into the process. It already checks other things under the proc lock, so it costs nothing to be completely correct in this case. -- John Baldwin
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