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Date: Fri, 17 Jan 2014 08:51:03 -0800 From: "H. Peter Anvin" <hpa@...or.com> To: Borislav Petkov <bp@...en8.de>, "Ren, Qiaowei" <qiaowei.ren@...el.com> CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "x86@...nel.org" <x86@...nel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Steven Rostedt <rostedt@...dmis.org> Subject: Re: [PATCH 2/5] x86, mpx: hook #BR exception handler to allocate bound tables On 01/17/2014 08:47 AM, Borislav Petkov wrote: > > Right, so Steve and I played a couple of scenarios in IRC with this. So > #BR is comparable with #PF, AFAICT, and as expected we don't take any > locks when handling page faults in kernel space as we might deadlock. > > Now, what happens if a thread is sleeping on some lock down that > GFP_KERNEL allocation path and another thread gets a #BR and goes that > same mmap_pgoff path and tries to grab that same lock? It goes to sleep. Same as if we take a page fault and have to page something in. > Also, what happens if you take a #BR in NMI context, say the NMI > handler? You should never, ever do that. We should never take a #BR in the kernel, full stop -- if we do it is panic time. > All I'm trying to say is, it might not be such a good idea to sleep in a > fault handler... A fault handler from user space is really nothing other than a different kind of system call. It is nothing magic about it. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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