Messages in this thread | | | Date | Fri, 18 Oct 2002 12:30:04 -0700 | From | george anzinger <> | Subject | Re: [RFC][PATCH] linux-2.5.34_vsyscall_A0 |
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Linus Torvalds wrote: > > On Fri, 18 Oct 2002, Andrea Arcangeli wrote: > > > On Fri, Oct 18, 2002 at 09:45:41AM -0700, george anzinger wrote: > > > Stephen Hemminger wrote: > > > > current cpu (and maybe current pid) somehow. And it would be possible > > > > to avoid preemption while in a vsyscall text page, some other Unix > > > > variants do this to implement portions of the thread library in kernel > > > > provided user text pages. > > > > > > > Now there is an idea! Lock preemption in user space if and > > > > sounds not good to me, you would miss a wakeup and you would delay the > > schedule of 1/HZ in the worst (close to the common) case. > > That's not the real problem. > > The real problem is that somebody can jump into the middle of a function > (or even into the middle of an instruction), causing the function to do > something totally different from the intended effect. > > In particular, it can cause the function to loop forever. > > If you disable preemption of user space, you now killed the machine. > > In short - others may do it, but it's a total _DISASTER_ from a security > and stability standpoint. Don't go there.
Oops, hadn't thought of that. Back out, undo, etc. :)
-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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