Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752608AbaG2H4K (ORCPT ); Tue, 29 Jul 2014 03:56:10 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:42179 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751044AbaG2H4I (ORCPT ); Tue, 29 Jul 2014 03:56:08 -0400 Date: Tue, 29 Jul 2014 09:55:36 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: Re: [PATCH RFC tip/core/rcu 2/9] rcu: Provide cond_resched_rcu_qs() to force quiescent states in long loops Message-ID: <20140729075536.GZ19379@twins.programming.kicks-ass.net> References: <20140728225556.GA19493@linux.vnet.ibm.com> <1406588180-21933-1-git-send-email-paulmck@linux.vnet.ibm.com> <1406588180-21933-2-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="XGMVbVQaXwwZxfEN" Content-Disposition: inline In-Reply-To: <1406588180-21933-2-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --XGMVbVQaXwwZxfEN Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jul 28, 2014 at 03:56:13PM -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" >=20 > RCU-tasks requires the occasional voluntary context switch > from CPU-bound in-kernel tasks. In some cases, this requires > instrumenting cond_resched(). However, there is some reluctance > to countenance unconditionally instrumenting cond_resched() (see > http://lwn.net/Articles/603252/), No, if its a good reason mention it, if not ignore it. > so this commit creates a separate > cond_resched_rcu_qs() that may be used in place of cond_resched() in > locations prone to long-duration in-kernel looping. Sounds like a pain and a recipe for mistakes. How is joe kernel hacker supposed to 1) know about this new api, and 2) decide which to use? Heck, even I wouldn't know, and I just read the damn patch. --XGMVbVQaXwwZxfEN Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJT11N4AAoJEHZH4aRLwOS6JDAP/2ENQDhPn17kIGLJsXwskbSp aB2aB9DithSPVPAVptBHbH+HNskQWkRA5hR5sDqVFb+cXRM1QiVbPKHhLjs2cGfh 21jHqGX75ZsrJB6yWeyGTJbNQUdSvE+skr3WWwuVUEFMYKXQX5c6/1gxvZIB/OLM 7AIriiUSBnjLzxGRHddMD2srgqaSE4NEYLD+xSZJbP2aoafi08oqmZhycMu8YqCE t9ZV2XuMfOzoTGPtmECww4AIAVB6Qu6l6k16ZWpKBs0MDr/41MTGTxbcnlFBQXRK Ce4o/V383rQjaCCueUn8GuXV7xAk59MrwrVgpT9W5ufLUA2BfT4Zmy38MfPhn3ht ly94cukUebRwIJ3wTGMMrXK7TtWuHLOVaFrCmHL6SAENEurtzR3gkv1EnMbPrxzO xA72mtULYVNSm/WwvdKSdWQrmXAZ4b1rBoGisKIDq2g+SJaqZSxDlmNSXgPXfbDJ wcM3ACIC9nzbDeTq0PdtXNgrEMlLYpP2PLK5NE0a/4HhyCK0vkO+DyDT4hP9ehin Bj1xEc1ar75hCuqdxqoAHSB/VxE5Yi9AJJl8jiTeq8pPew4isheKUm/sW46yP1bQ Ryfbc6WKx/TRJbq6cwj5SguAMzFwnp+t7aT7Mip1t6Qrfe6/0/k8zUTH7ErpcgR8 dO/vnajtxDJRA6x5MN3U =uyUj -----END PGP SIGNATURE----- --XGMVbVQaXwwZxfEN-- -- 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/