Date: Thu, 21 Oct 2004 23:37:00 -0400 From: Brian Fundakowski Feldman <green@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: Julian Elischer <julian@elischer.org> Subject: Re: PERFORCE change 63396 for review Message-ID: <20041022033700.GL1072@green.homeunix.org> In-Reply-To: <200410201258.26325.jhb@FreeBSD.org> References: <200410192159.i9JLxNLE003024@repoman.freebsd.org> <417592DB.6050609@elischer.org> <200410201258.26325.jhb@FreeBSD.org>
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On Wed, Oct 20, 2004 at 12:58:26PM -0400, John Baldwin wrote: > On Tuesday 19 October 2004 06:19 pm, Julian Elischer wrote: > > John Baldwin wrote: > > >http://perforce.freebsd.org/chv.cgi?CH=63396 > > > > > >Change 63396 by jhb@jhb_tibook on 2004/10/19 21:58:24 > > > > > > Update. > > > > > >Affected files ... > > > > > >.. //depot/projects/smpng/sys/notes#21 edit > > > > > >Differences ... > > > > > >==== //depot/projects/smpng/sys/notes#21 (text+ko) ==== > > > > > >@@ -33,6 +33,10 @@ > > > - Untested > > > - Don't allow kthreads to get signalled and do bad things > > > - Untested > > >+- Change amd64 to use [ls]fence instructions for memory barriers. > > >+ - Untested (and no hardware, maybe peter can test) > > >+- Turn off the ipiwakeups in 4BSD since the currently implementation can > > >+ lead to IPI deadlocks > > > > the implementation of IPIs or the implementation of IPIwakeup? > > Kind of hard to say. The problem is if a CPU tries to send two IPI_AST's > without enabling interrupts in between. The first IPI may not be delivered > when the second one is requested because the target of the first IPI has > interrupts disabled for some reason (doing a TLB shootdown is the worst case > scenario). The other CPU won't enable interrupts to allow the first AST > until it's shootdown is acknowledged. Since the first IPI is never > delivered, then the second IPI attempt will never be able to deliver an IPI, > resulting in either a panic or deadlock. My quad xeon is highly unstable on > HEAD, btw, and this does seem to help it. Isn't this what I said a few weeks ago was probably the problem? -- Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\ <> green@FreeBSD.org \ The Power to Serve! \ Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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