From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id C27942C00A8 for ; Mon, 13 May 2013 19:06:51 +1000 (EST) Message-ID: <1368435991.19924.35.camel@pasglop> Subject: Re: [RFC PATCH v3 2/5] powerpc: Exception hooks for context tracking subsystem From: Benjamin Herrenschmidt To: Li Zhong Date: Mon, 13 May 2013 19:06:31 +1000 In-Reply-To: <1368434680.2618.33.camel@ThinkPad-T5421> References: <1368422493-9831-1-git-send-email-zhong@linux.vnet.ibm.com> <1368422493-9831-3-git-send-email-zhong@linux.vnet.ibm.com> <1368424667.19924.26.camel@pasglop> <1368434680.2618.33.camel@ThinkPad-T5421> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: fweisbec@gmail.com, linux-kernel@vger.kernel.org, paulus@samba.org, paulmck@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2013-05-13 at 16:44 +0800, Li Zhong wrote: > Yes, the above and hash_page() are two C functions for a same exception. > And the exception hooks enable RCU usage in those C codes. But for asm > codes, I think we could assume that there would be no RCU usage there, > so we don't need wrap them in the hooks. hash_page() won't start a new RCU, at least not in its current incarnation, the only thing I can see it ever doing would be to take some RCU read locks one day (it doesn't today). low_hash_fault() is a different beast. It will typically kill things, thus involving sending signals etc... RCU might well be involved. Cheers, Ben.