From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <018fd7d22990276158c51cac837d041b@quanstro.net> From: erik quanstrom Date: Thu, 16 Apr 2009 18:19:01 -0400 To: 9fans@9fans.net In-Reply-To: <9ab217670904161449s715246f0te2c24244e9c9865a@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Subject: Re: [9fans] security questions Topicbox-Message-UUID: ded3fb42-ead4-11e9-9d60-3106f5b1d025 On Thu Apr 16 17:51:42 EDT 2009, devon.odell@gmail.com wrote: > 2009/4/16 erik quanstrom : > > have you taken a look at the protection measures already > > built into the kernel like smalloc? > > At least in FreeBSD, you can't sleep in an interrupt thread. I suppose > that's probably also the case in Plan 9 interrupt handlers, and this > would mitigate that situation. plan 9 doesn't have interrupt threads, but that's beside the point. interrupts are driven by the hardware, not users. so smalloc, which is used to allow user space to wait for memory if it is not currently available doesn't make any sense. having the potential for running out of memory in an interrupt handler might be a sign that a little code reorg is in order, if you are worried about this sort of thing. (and even if you're not.) in any event, i think there is more code to deal with these problems in the kernel that first meets the eye. much of it is small and, if you're not looking for it, easy to miss. > Depends again on the application. If you're talking about a terminal, > yes. If you're talking about a CPU server where someone is working on > code, someone else is writing a presentation, and yet another person > is in the middle of a video transcode, you're talking about a lot of > wasted time, potentially. and potentially, i could win the lottery. ☺. i have had exactly 1 out-of-resource reboot in the last 18 months. without real data on what and where the problems are, i would think this would become a difficult issue. - erik