Date: Sun, 11 Nov 2007 20:34:43 -0800 From: Julian Elischer <julian@elischer.org> To: Marcel Moolenaar <xcllnt@mac.com> Cc: Kostik Belousov <kostikbel@gmail.com>, Alexander Motin <mav@FreeBSD.org>, freebsd-arch@FreeBSD.org Subject: Re: Kernel thread stack usage Message-ID: <4737D7E3.3090500@elischer.org> In-Reply-To: <06618562-A789-4B5E-94BF-0ED8AB51A1FF@mac.com> References: <1191187393.00807485.1191175801@10.7.7.3> <1191189248.00807488.1191177603@10.7.7.3> <4736D8AF.7010209@FreeBSD.org> <20071111163815.GJ37471@deviant.kiev.zoral.com.ua> <47373C5E.2080800@elischer.org> <0414590D-0C2A-4EBD-9617-7AC193ABD1E8@mac.com> <4737696A.7050605@FreeBSD.org> <06618562-A789-4B5E-94BF-0ED8AB51A1FF@mac.com>
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Marcel Moolenaar wrote: > > On Nov 11, 2007, at 12:43 PM, Alexander Motin wrote: > >> Marcel Moolenaar wrote: >>> This is not theoretical at all: On ia64 there are 2 stacks. One >>> growing down and one growing up. The downward stack is used for >>> stack-based variables and the pward growing stack is used by >>> the processor for stacked registers. >> >> Hmm, interesting. And which one is pointed by td_kstack there? Or they >> are using same segment but from opposite sides? > > The latter. The td_kstack variable points to the bottom, > which is where the register stack starts. The memory stack > start from td_kstack + td_kstack_size. > >>> The code suggested will not be meaningful on ia64. >> >> Why? If variable stack growing down and it's segment is pointed by >> td_kstack then where is the problem? Or you mean that system will die >> earlier when those two stacks in same segment will reach each other? > > It's the register stack that grows faster in general and > yes, they grow towards each other so they can eventually > run into each other. > so one could write something that detects tha tyou are getting close, but it would have to be machine dependent..
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