From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1XXUjs-0006Vc-Ol for user-mode-linux-devel@lists.sourceforge.net; Fri, 26 Sep 2014 12:35:08 +0000 Received: from rcdn-iport-6.cisco.com ([173.37.86.77]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1XXUjr-0000lX-Nl for user-mode-linux-devel@lists.sourceforge.net; Fri, 26 Sep 2014 12:35:08 +0000 From: "Anton Ivanov (antivano)" Date: Fri, 26 Sep 2014 12:35:01 +0000 Message-ID: <54255D73.1030509@cisco.com> References: <1411732166-653849-1-git-send-email-anton.ivanov@kot-begemot.co.uk> <5425547C.1080002@nod.at> In-Reply-To: <5425547C.1080002@nod.at> Content-Language: en-US Content-ID: <2DCC713F1B656043961679DFA3382354@emea.cisco.com> MIME-Version: 1.0 List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net Subject: Re: [uml-devel] [PATCH] Fix for "occasional userspace process in D/Z state" bug To: Richard Weinberger , "anton.ivanov@kot-begemot.co.uk" , "user-mode-linux-devel@lists.sourceforge.net" Cc: Daniel Walter On 26/09/14 12:56, Richard Weinberger wrote: [snip] > +#ifdef CONFIG_X86_32 > + alternative("lock; addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2); > +#else > + asm volatile("mfence":::"memory"); > +#endif > Why not mb()? > I'm not sure whether this fix is correct. Looking at the actual defines that would work. I was originally looking at asm-generic instead of x86/um/asm/barrier.h and the asm-generic barrier() would have been insufficent. x86/um/asm/barrier.h has literally the same define, so as you noted - using mb() will have the same effect. As far as is this fix correct or not - I do not know myself. I said it when submitting it :) It definitely fixes the problem - both the original (and extremely difficult to reproduce) D|Z in the stock UML and the similar (and much easier to reproduce) D|Z which you get with all the disk subsystem improvement patches. I will reissue it with mb() shortly. A. > > Thanks, > //richard ------------------------------------------------------------------------------ Meet PCI DSS 3.0 Compliance Requirements with EventLog Analyzer Achieve PCI DSS 3.0 Compliant Status with Out-of-the-box PCI DSS Reports Are you Audit-Ready for PCI DSS 3.0 Compliance? Download White paper Comply to PCI DSS 3.0 Requirement 10 and 11.5 with EventLog Analyzer http://pubads.g.doubleclick.net/gampad/clk?id=154622311&iu=/4140/ostg.clktrk _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel