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On Fri, 6 Feb 2004 17:28:36 +0530 "Amit S. Kale" <amitkale@emsyssoft.com> wrote: > On Friday 06 Feb 2004 7:50 am, Andi Kleen wrote: > > On Thu, 5 Feb 2004 23:20:04 +0530 > > > > "Amit S. Kale" <amitkale@emsyssoft.com> wrote: > > > On Thursday 05 Feb 2004 8:41 am, Andi Kleen wrote: > > > > Andrew Morton <akpm@osdl.org> writes: > > > > > need to take a look at such things and really convice ourselves that > > > > > they're worthwhile. Personally, I'd only be interested in the basic > > > > > stub. > > > > > > > > What I found always extremly ugly in the i386 stub was that it uses > > > > magic globals to talk to the page fault handler. For the x86-64 > > > > version I replaced that by just using __get/__put_user in the memory > > > > accesses, which is much cleaner. I would suggest doing that for i386 > > > > too. > > > > > > May be I am missing something obvious. When debugging a page fault > > > handler if kgdb accesses an swapped-out user page doesn't it deadlock > > > when trying to hold mm semaphore? > > > > Modern i386 kernels don't grab the mm semaphore when the access is >= > > TASK_SIZE and the access came from kernel space (actually I see x86-64 > > still does, but that's a bug, will fix). You could only see a deadlock when > > using user addresses and you already hold the mm semaphore for writing > > (normal read lock is ok). Just don't do that. > > OK. It don't deadlock when kgdb accesses kernel addresses. > > When a user space address is accessed through kgdb, won't the kernel attempt > to fault in the user page? We don't want that to happen inside kgdb. Yes, it will. But I don't think it's a bad thing. If the users doesn't want that they should not follow user addresses. After all kgdb is for people who know what they are doing. -Andi - 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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