From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Date: Sat, 20 Nov 2004 07:45:18 +0000 Subject: touch_nmi_watchdog (was: page fault scalability patch V11 [0/7]: Message-Id: <419EF60E.4030006@yahoo.com.au> List-Id: References: <20041120020306.GA2714@holomorphy.com> <419EBBE0.4010303@yahoo.com.au> <20041120035510.GH2714@holomorphy.com> <419EC205.5030604@yahoo.com.au> <20041120042340.GJ2714@holomorphy.com> <419EC829.4040704@yahoo.com.au> <20041120053802.GL2714@holomorphy.com> <419EDB21.3070707@yahoo.com.au> <20041120062341.GM2714@holomorphy.com> <419EE911.20205@yahoo.com.au> <20041120071514.GO2714@holomorphy.com> <419EF257.8010103@yahoo.com.au> In-Reply-To: <419EF257.8010103@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: William Lee Irwin III Cc: Linus Torvalds , Christoph Lameter , akpm@osdl.org, Benjamin Herrenschmidt , Hugh Dickins , linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org Nick Piggin wrote: >> (2) NMI's don't nest. There is no possibility of NMI's racing against >> themselves while the data is per-cpu. >> > > Your point was that touch_nmi_watchdog() which resets alert_counter, > is racy when resetting the counter of other CPUs. Yes it is racy. > It is also racy against the NMI on the _current_ CPU. Hmm no I think you're right in that it is only a problem WRT the remote CPUs. However that would still be a problem, as the comment in i386 touch_nmi_watchdog attests.